by Robert Monaghan ver. 1.2 (5/2000)
Sharp Center or Edges?
Sharp Center or Edges?
Related Link:
Body Focus Errors in 8 of 10 New Cameras [2/2003]
Film Flatness in TLRs (photo.net thread) [2/2001]
Focus problems in medium format: The article they wouldn't.. print
Motor Drive Second Shot Blur Problem
(Grumpy's site) {flatness issue} [10/2000]
Why No Camera Can Focus (Precisely) [8/2000]
| MF/LF Lens Tester Chris Perez on Medium Format Flatness Issues |
|---|
| It appears that film flatness is a serious issue with some medium format cameras. It appears that 120 film "bows" in the middle of the pressure plate for nearly all cameras tested. It shows up most frequently when shooting 6x9 (2 1/4 x 3 1/4) format cameras and film backs |
Depth of focus usually masks the effects of such
flatness errors above f/5.6 (on 35mm). But many of the soft focusing
errors found in using faster f/stops may be due to film flatness
issues rather than photographer focusing errors. Unfortunately, modern
technology such as autofocus won't solve
problems due to film bulging at the film plane.
| Large Format is limited by film flatness... |
|---|
| 35mm is limited by film quality, while LF is limited by film flatness and the need to use small apertures |
I find surprisingly little discussion about film flatness online or
on paper. We argue a lot about which lenses are better, with slightly
better resolution or sharpness (in lpmm) and contrast. Yet film flatness
problems can turn an expensive lens into a mediocre performing one, and
cost us half our contrast or more. Isn't that worth some study?
Film is supposed to be flat. Lenses are curved. Curved
lenses have
to be very, very highly corrected to produce a truly flat image on film.
Unfortunately, most real-world lenses suffer from some degree of field
curvature
of their projected image plane. This lens field curvature is greatest in
wide angle lenses, and usually least in long telephoto lenses.
The result is that we are trying to project an image surface that is
curved in space onto a supposedly flat film plane.
But since 35mm and medium format SLR cameras are typically used with a
variety of lenses, you can't optimize your camera focusing setup for one
type of lens curvature over another. So you have a compromise, one
which means that you can't get the optimal sharpness out of the usual
range of lenses you use.
Your camera system designer has a basic choice:
Most camera system designers strive for a compromise in which both the
center and the edges are reasonably sharp. But lens field plane curvature
means that approach is a compromise in most cameras.
The above graphic (inspired by Keppler's article in August 1968 Modern
Photography, p.29, 31) shows how you can get
optimal sharpness in the center, but only if you blow off edge sharpness.
Similarly, you can get the edge sharpness quite high, but only by
ignoring the softness in the central part of the film image. So most
lens designers compromise, reducing central sharpness significantly in
order to achieve a reasonable compromise in edge sharpness.
In the top section of Keppler's table below, the curved image is set to
just touch the film ("center sharp" in our graphic above). The 50mm lens
turns in a very good to excellent performance in the center - but the
edges are much poorer. Now offset the film or plane of focus by 1/2,000th
of an inch (0.0127 mm) and you get the compromise performance shown in
the lower half of the table below. In general, all the edge values have
been upgraded one level, while the center sharpness has been dropped one
level, and you have the typical compromise of today's optics.
| 50mm lens set for center sharpness | ||
| aperture | center sharpness | edge sharpness |
| f2 | very good | not acceptable |
| f2.8 | very good | not acceptable |
| f4 | very good | acceptable |
| f5.6 | excellent | good |
| f8 | excellent | good |
| f11 | very good | good |
| f16 | very good | acceptable |
| 50mm lens set for compromise | ||
| aperture | center sharpness | edge sharpness |
| f2 | good | acceptable |
| f2.8 | good | acceptable |
| f4 | good | good |
| f5.6 | very good | very good |
| f8 | very good | very good |
| f11 | good | very good |
| f16 | good | good |
What if you can't interchange screens on your camera? Or suppose you
really need maximum center sharpness with your regular lenses? Keppler
cites a trick suggested by noted camera repairman Marty Forscher.
Household cellophane tape is just about 1/2,000th of an inch thick. A
single layer on the film guide rails of camera (the inner ones on which
the film travels, not the outer channel rails) will move your film
forward that magical 1/2,000th of an inch too. It may be worth a try, and
its cheap and easy to undo (careful with any solvent!).
As we have seen with the Novoflex long
telephoto lenses, if you opt for center sharpness and let the edges
go you can get very impressively sharp central regions. This approach
works with long telephotos, where we often have to enlarge from the
center of the image for cropping and further magnification anyway.
You may also recall that long telephotos tend to have the flattest lens
curvature. So the falloff, while drastic, is much less than it
would be with a more inherently curved field lens design (e.g., wide angle).
I have also seen some Vivitar 35mm lens tests in which the edge performance
was very good to excellent, while the center sharpness was rated a grade
or so lower on average. However, the rating systems (Modern Photography
and Popular Photography) are skewed - a lens lpmm value that would be
very good in the center would be excellent in the edges. So what I
first thought to be an odd-ball optical anomaly was actually just a
series of low-cost lenses which were optimized for relatively
flat resolution performance.
But beware if you are using the older grade (rather than lpmm) scales
used in lens test tables in Popular Photography and Modern Photography, as
the standards for edge sharpness may be less than for the center to
receive the same top ratings! This approach is more a result of the
problems of getting good edge performance for some of the reasons (lens
field curvature..) discussed here.
Finally, carefully designed and built macro-lenses tend to do best at
maintaining essentially flat sharpness with similar lpmm values in both
the lens center and edges. On our Diopter Lens
page, we have a table showing this comparison for a 100mm f/4 SMC
Macro-Takumar (Pentax) lens.
This lens had the lowest linear distortion (0.7%) and flat resolution (56
lpmm center and edge) with little color fringing. But many low cost zooms
and the other primes had higher center sharpness, falling down only in
their edge sharpness well below the flat resolution of the macro-lens. So
you can get a highly corrected flat-field lens with similar center and
edge resolution. But it is usually a compromise in which center sharpness
has been reduced somewhat, rather than one in which the edge sharpness is
brought up while leaving the center sharpness uncompromised.
The above macro lens sharpness comparison table is also surprising in
that a closeup lens (2 element) plus prime lens (nikkor 50mm f/1.4) had
the highest central sharpness (88 lpmm) and high edge sharpness (50 lpmm)
with moderately low distortion, lateral color, and astigmatism (beating
extension tubes on the same lens!). For many of us doing nature closeups,
this lower cost approach is much sharper than the compromise macro-lens
approach.
So when I need to copy documents or artwork, I reach for my
flat-field or macro lenses. But when I do nature closeups, I'm not
ashamed of using a decent 2 element achromatic closeup lens. I am in
effect redesigning my own (macro) lens in which I am optimizing center
sharpness (to 88 lpmm!) for nature work, rather than accepting the
"dumbed-down" compromises needed to create a flat-field (and usually
less-sharp overall) macro-lens with good edge sharpness and linearity.
| ... |
|---|
| Readers will recall John Winchcomb's report some while back (BJP 15 Dec. 1999) documenting the effect that kinks, introduced by bends in the film path, have on the recorded sharpness of roll film images. His tests proved that this is a genuine effect, which not only degrades image quality but also does so in a non-uniform manner. Therefore, the tactic of preloading and winding on your film inserts that feature 'bent' film paths (as are fitted into most other brands of medium format cameras) is one that quality conscious photographers should treat with great caution... |
I think this view is probably at least partially correct, but Leitz lenses
have another secret factor going for them. These lenses have a high degree
of care taken to ensure precise centering of the lens. Centering and
alignment is obviously critical if tolerances are to be minimized and
sharpness maximized. Such expensively aligned lenses may be significantly
sharper when elements are hand-picked to maximize performance (as on many
Leitz and Zeiss lenses). (See lens and glass
manufacturing pages)
I have elsewhere explored some of the variations in lens batches. Obviously, lenses
are made of parts with various tolerances (albeit often small).
Sometimes, these tolerances come together and add up, giving you a lemon
of a lens. At other times, these tolerances cancel out, and you get the
lens optimally performing as defined by its designer. So in any batch of
lenses, some are better, sharper, and more contrasty than others.
These same lens tolerances impact the relative flatness of the projected
image and its actual curvature.
| Bronica 6x6cm Film Flatness Trick |
|---|
| Film flatness all across the format must be maintained to much less than the 0.005 inch tolerance*. To aid in this the Bronica has a spring-loaded bar which presses the film and pulls it taut. This bar is situated just outside the film aperture between two small guide rollers. It is actuated whenever the film drive is stopped. [*ordinary typing paper is 0.003-0.004"] |
| Effect on contrast of film bulges on 35mm | ||
|---|---|---|
| test conditions: | film bulge | Effect on Contrast |
| advance and shoot | 0.08mm | 48% drop in contrast |
| advance, wait 30min, shoot | 0.04mm | 14% drop in contrast |
This table presents some pretty useful information. Do you take a whole
series of shots, one right after the other (maybe bracketing), then stop
until the next good shot comes along? If so, you probably have the worst
exposure to film bulge effects since your film doesn't have time to
"relax" and flatten out once out of the film cartridge.
On the other hand, if you wait, you may find that you get better results
after your film has been advanced and allowed to "relax" and flatten out
before shooting.
So if you currently take an exposure, then wait until the next shot comes
up to advance the film, think again. Yes, maybe that does help prevent
unwanted exposures in some cameras. But it may also guarantee you get the
most film bulging using that film winding approach. Based on this data,
it may be better to advance the film right after you shoot so as to let
it "relax" and flatten out.
I also advocate the above approach as it warns you when you are out of
film hopefully before that flying saucer zooms by your head and is gone
before you can reload! It also means you are ready to shoot in an instant
if a shot comes up suddenly, without having to wind film first.
Try shooting a tripod mounted shot right after advancing film, and again
after 20 or 30 minutes have gone by. Use identical settings. Do you see
any differences in contrast or sharpness between the shots? If you do,
you may now have an explanation for why that happens.
Note that film curling also varys somewhat with where the film is in the
roll, tightness of your film winding, and related factors. When loading
film, I personally
always rewind backwards on the rewind crank (35mm camera) until the slack
in the 35mm film in the film cannister is taken up. One reason I do this
is so I can watch when I advance the film. If the film is advancing
properly, then I will see the film rewind lever move around as the film
is advanced. If I don't, the film is mis-aligned and perhaps not feeding
properly. But this approach also helps put some tension on the film and
helps ensure that the film will be flatter in its channel, and hopefully
flatten out faster too between shots.
A few medium format cameras such as the Kowa 66
have patented designs which don't involve such radical film bending, and
reportedly help improve film flatness. The Koni-Omega 6x7cm rangefinders also feature a
straight-thru back design with a pressure plate that lifts during film
advance to prevent film scratching.
Some recent postings suggest that maximum film
flatness in medium format is achieved by delaying advancing
film until
right before shooting. This recommendation is opposite to that for 35mm
film, again due to the differences between 35mm film cartridges and
rollfilm back designs.
Similarly, the same postings note that use of 220
rollfilm rather than 120 rollfilm improves flatness, even without the use
of a vacuum back (see related notes herein). Some recent articles (August
1999) in The British Journal of Photography echo this
recommendation to use 220 film. In their study, the 220 film was more
precisely positioned at the correct film plane in the backs they studied,
yielding higher resolution (lines per millimeter) imagery on 220 film than
on 120 film.
So with medium format, in contrast to 35mm film cartridges, it may be best
to wait until right before you make the exposure to advance the film. This
approach may make it harder to double expose film, which some medium
format cameras make easy to do in error (e.g., Mamiya press). You will
simply have to keep a spare film back loaded with film and ready to mount
in case that flying saucer shows up overhead!
| The conclusions are clear. Firstly, 220 film will give potentially superior results to those of 120 film. Secondly, film positioning errors and distortion undermine the potential benefit of the MF camera; use of 220 film can help to offset these errors a little. And thirdly, the errors demonstrate that the camera may not produce its optimum performance on the focused plane, and that best sharpness may occur randomly on non-focused planes. As a result of these observations, there is clearly a good case for film makers to produce a 12 frame version of 220 film. Equally, camera makers could do surely more to release the full potential of their lenses by improved film positioning performance. Source: Roll with It by John Winchcomb, British Journal of Photography, December 15, 1999, pp. 20-1. |
The above article carried some doubly surprising scans of a number of test rolls of 120 slide
film (ektachrome) and 220 FP4+ negative film. The big shocker was the observation that many of
the film surface scans put the 120 paper backed films some 0.005 inches away from the film plane.
That is a huge built-in focusing error. The 220 film had a displacement less than half this value.
Quoting the above cited article again [p.20], An error of 0.005 inch (0.127mm)
as is typical in Graph 1 [ed. note: 120 ektachrome scan], using an 80mm taking lens focused
at a distance of 10 meters, yields a field error of more than 1.5 meters.!
Wow! In other words, the focus position of the 120 film is shifted a distance which corresponds to
a focusing error of 1.5 meters at 10 meters or roughly five feet error at 33 feet. Being five feet
off in focus at 33 feet is a huge error on an 80mm lens!
The 220 film that was loaded, advanced without delays, and immediately scanned showed the least film buckling. The 120
film showed more buckling at the edges of the frame, in some cases an large 0.008 inches (or
more than 2 meters error at 10 meters focusing distance). The 220 and 120 film which were allowed
to sit showed a large degree of kinking and buckling, especially at the edges of the film which
is also nearest the rollers. Even on the 220 film, this buckling reached 0.006 and 0.008 inches
respectively on each side of the film scanned area.
An 80mm f/2.8 lens on a 6x6cm SLR focused at 33 feet (10 meters) has a near DOF point of 26 feet
and a far distance of 44.8 feet. For an f/2.0 lens, make that 28 ft and 41 feet. Now you know
one reason fast lenses are problematic in medium format!
In color film, the exposed grains of silver attach the appropriate dye
particles, producing a larger "blob" than just the exposed silver grain
alone. Kodachrome is an exception, which helps explain its legendary
sharpness over other color films. In Kodachrome, the dyes precisely
replace the exposed silver grains, molecule for molecule, so there is no
increase in size of the resulting dye "grains". So due to its unique
and complex chemistry, Kodachrome slides tend to be sharper than other
simpler chemical process alternatives.
Mr. Goldberg also makes the point that lenses often have some small
mis-alignment in their mountings (e.g., barrel). If the lens optical axis
doesn't match the camera's alignment (i.e., film plane), then you may get
a tipped (non-symmetric) plane of sharpness through your film. For
example, the right side might be very sharp, the center less sharp, and
the left side unacceptable.
How can you test for this problem? Mr. Goldberg suggests you try the
usual lens tests (e.g., brick wall on a tripod), only add this extra test
shot. Turn the camera upside down, and take a second shot. Compare the
sharpness of the two slides. If they differ, you may have just diagnosed
a lens axis alignment problem.
| Depth of Focus | ||||
|---|---|---|---|---|
| format= | 35mm | 6x4.5 | 6x6 | 6x7 |
| CoC= | 0.03 | 0.05 | 0.06 | 0.065 |
| f/stop | depth of focus (in mm) | |||
| 1 | 0.06 | 0.1 | 0.12 | 0.13 |
| 1.4 | 0.084 | 0.14 | 0.168 | 0.182 |
| 2 | 0.12 | 0.2 | 0.24 | 0.26 |
| 2.8 | 0.168 | 0.28 | 0.336 | 0.364 |
| 4 | 0.24 | 0.4 | 0.48 | 0.52 |
| 5.6 | 0.336 | 0.56 | 0.672 | 0.728 |
| 8 | 0.48 | 0.8 | 0.96 | 1.04 |
| 11 | 0.66 | 1.1 | 1.32 | 1.43 |
| 16 | 0.96 | 1.6 | 1.92 | 2.08 |
| 22 | 1.32 | 2.2 | 2.64 | 2.86 |
| 32 | 1.92 | 3.2 | 3.84 | 4.16 |
| 45 | 2.7 | 4.5 | 5.4 | 5.85 |
| 64 | 3.84 | 6.4 | 7.68 | 8.32 |
Now if film varys by an average of 0.2mm from being flat, and on a
majority of 35mm and medium format cameras, what does that mean? From the
depth of focus table above, you can see that total depth of focus
is very shallow for f/stops below f/2.8 for typical CoC values (CoC=
circles of confusion, in mm). Actually, things are even worse than might
appear, since we usually place the ideal film plane at the center of the
total depth of focus, splitting the total range in half. So
dividing the
above table entries in half gives you some idea of how far you can vary
on either side from being flat and still have depth of focus cover the
divergence. One wonders if the lack of fast medium format lenses (below
f/1.9 for 6x4.5cm and f/2 for 6x6cm) is due more to limitations in film
flatness than optical design limitations.
Granted, film buckling may only seriously effect 60% of the 35mm SLRs and
almost all 6x6cm medium format SLRs (see notes below). But that still
helps explain why so many photographs are not sharp, especially when the
lens is focused wide open. It is not just focusing accuracy and the
limited depth of field in front of the lens. The depth of focus behind the
lens is also limited, especially wide open. So errors in focusing you may
now be blaming on yourself for mis-focusing may be due in part to film
buckling, based on these figures and estimates.
Depth of focus is another reason why stopping down helps improve the
sharpness of our images on film. Our depth of focus table above shows how
you get more depth of
focus as well, which covers up film buckling effects more than when the
same lens is used wide open.
What does this mean? Keppler's 1/2,000th of an inch screen shift is only
12.7 microns. Yet we have reports below of film buckling estimates of
0.2mm or 200 microns, sometimes much more! But the film must be flat
within 12.7 microns or suffer some loss in sharpness or resolution (as
measured by lpmm) and contrast. Above f/4, depth of focus may minimize the
impact of a 0.2mm film bulge (on 35mm). But watch out if you are using
fast lenses (f/1.4 or f/2) at faster apertures with a similar
"average" 0.2mm film
bulge!
Most manufacturers and photographers ignore film buckling and bulges,
hoping that any errors will be hidden by depth of focus. See above for
our depth of focus table and posts below on the calculation of depth of
focus and related tables.
But as we have seen, depth of focus only provides a modest "slop" factor
(See depth of focus table above). A tiny 1/2,000th inch (12.7 micron)
shift in the film position, or buckling of part of the film, can cause the
drop in sharpness reported by Keppler. Now if 1/2,000th of an inch (12.7
microns) can raise or lower your lens central or edge sharpness by a full
grade (e.g., very good to good), what would 0.2mm (or 200 microns) of film
buckling do?
Similarly, a 0.08mm film bulge (from rapidly advancing film
without time to flatten out) can reduce contrast by circa 48% (see
Goldberg notes and table above). See why I'm concerned about film
flatness?
Conversely, enhancing film flatness might mean securing the extra
performance that it costs very high dollars to design and build into your
premium lenses. Some camera models (e.g., Rollei, Contax, Linhof) have
vacuum devices which help to suck film flat at the instant of exposure.
If film flatness isn't important, then why are the top manufacturer names
in photography spending such sums developing these vacuum back film
flattening tricks?
On 35mm cameras, we have an unstandardized and variablely designed film
lip on the
so-called standard film cassette. This generally curved lip and circular
film cassette design means that 35mm film is often more subject to
curving as it comes out of the film cassette. Here again, some
photographers claim to be able to see differences in film that is
advanced and immediately exposed, versus film that is advanced and
allowed to "relax" and flatten out.
Some photographers have reported better results when using the old-style
reloadable bulk-film cassettes from Nikon. These designs use a film gate
opening that doesn't impart the degree of lip curl of the typical 35mm
cassette.
As noted below, up to 60% of the tested 35mm and virtually all of the
6x6cm medium format film backs showed evidence of film buckling.
Another approach is described below. You can take thin glass and use it
to flatten the film against the film back. Mr. Maersk-Moller's approach
uses a thin glass plate to flatten the film. In a test case, an
unacceptable Biometar f/2.8 lens was improved from unacceptable to
excellent over most of its range by such a modification.
Film flatness is less of a concern when large f/stops (f/32 and above)
are used, as on large format cameras. Even here, Michael Gudzinowicz
below noted the benefits of using a glass plate carrier from an enlarger
to minimize film bowing (of circa 0.2mm or 200 microns) in a vertically
mounted large format copy or process camera.
But as Dirk Schmitt notes below, it is on 35mm cameras with their fast
lenses used wide open that film flatness becomes a real issue. Even the
Rollei SL35E cameras he used were "out of spec" on this flatness
parameter. Rollei's special film channel design is another effort to
minimize these deviations, and so improve sharpness performance on film.
The few hundredths of a millimeter (or few tens of microns) of film
flatness Dirk calculated correspond pretty well to the 1/2,000th of an
inch value cited by Keppler (for a drop of one rank in film
resolution, or circa 5 or so lpmm).
But try this test - I bet you will be really surprised!
You need a fast lens (50mm f/1.x) and a pencil, paper, and millimeter
ruler. Focus on an object (e.g., front of a car say 20 feet away, etc.).
Now put a pencil mark on your lens scale to mark the focused distance (it
will come off easily by rubbing, obviously). Turn the lens to infinity.
Refocus on the same object from the same place. Check the focusing point.
Is it exactly the same? Exactly? No, huh? Repeat this test 10 to 20 or
more times. What is the biggest range (in mm or in feet/meters from the
lens) that your focusing point is off. Don't cheat and focus
super-carefully, unless that's how you do it in casual photography too.
I'll bet you are surprised to see how inaccurate your focusing efforts
are, or more precisely, how much they varied, right?
This observation is one reason I like using the bright chimney finders
available for my Hasselblad and Bronica cameras. The 5x magnifying
finders make it a lot easier to focus accurately, as does the large
ground glass image.
I also have a pop-up magnifier that I use on some of my 35mm cameras
(unfortunately, one size doesn't fit all brands). This magnifier provides
a similar magnified image that is much easier to focus. I also tend to
rely more on my ground glass screen area for focusing accuracy. You may
notice that the focusing aids in some cameras will produce different
focusing points than the ground glass. I have found the ground glass
seems more accurate in my tests of who is right.
If you have ground glass, split line, and microprism aids, do you know
which one provides the most precise focusing on your camera?
In short, if you can't focus accurately to begin with, you can't get the
maximum sharpness out of your lens anyway. So while film flatness and
film buckling may be important in many situations, focusing accuracy
is always an issue for me!
We understand why a much thinner single black and white emulsion layer
can be much sharper than a multi-layer color emulsion. The black and
white layer is only circa 15 microns, versus up to 75 microns for some
color film emulsions. Yet just this difference alone is enough to provide
much of that measure of greater sharpness and lpmm resolution seen in
black and white film test results!
We understand why it is so hard to get precise and sharp focus when
lenses are used wide open. The depth of focus is very small, as little as
1/2,000th of an inch (12.7 microns) can result in a shift of lens
resolution (lpmm) of an entire grade (circa 5-10 lpmm shift). Consider
that many pricey lenses justify their higher costs on modest performance
improvements of this magnitude. Isn't it startling to learn that errors
in the focusing system of 1/2,000th of an inch can turn an expensive lens
into a much less expensive type performer?
We understand how some early lenses could turn in incredibly sharp
performances in lens resolution. The curvature of the lenses matched the
curvature of the film plane channel, producing a cancellation of errors
and offsets and optimal lens performance.
We can see how small tolerances of a few ten-thousandths of an inch can
cause such variations in lens performance between lenses of the same
batch. When you realize that the focusing system and film flatness are
critical to factors of 1/2,000th of an inch, you can see how such
seemingly tiny errors can radically impact on-film performance.
We understand how some lenses such as the legendary Novoflex optics can
perform so sharply in the center, but have such radical falloff in edge
sharpness.
I hope the various tests suggested above help you to improve your photo
efforts on film, and better understand some of the reasons lens and
on-film results seem to vary so much between photographers...
Editor's Note: the following section is from
Why is Large Format Resolution Lower than 35mm/MF?
Film Flatness:
Various sources have suggested that a typical maximum variation for film flatness in LF 4x5 film holders is anywhere from 0.2mm to 1mm. As Michael Gudzinowicz noted, face down (copy work), the bow which results is slightly less than 1 mm. He suggested a neat trick to control this film bowing, by placing the film between flat glass plates as with an enlarger negative carrier when used on a process (copy) camera. I suspect a more typical value is under 0.2mm on LF. The corresponding value for 35mm and MF film curling is typically under 0.05mm. Again, these factors shouldn't be surprising considering 4x5 film is physically much larger than 35mm or MF film and held in an open sheet film holder rather than a narrower film channel.
Film flatness is clearly a concern to some LF photographers, who purchase vacuum backs made by various manufacturers so as to minimize these errors and related problems. For the majority of LF users, film flatness isn't a major issue because the depth of focus highlighted above encompasses this error source too. But to achieve the desired depth of focus, we have to use high magnification of the ground glass image and careful focusing.
| Film Flatness Test |
|---|
|
The test of film flatness uses an illuminated grid with transparent lines
on a black background. The grid boxes are about one inch square. The
light is reflected onto a back of a 6x6cm SLR or film holder of a view
camera. By checking (and photographing) the pattern of the lines on the
film surface, you can observe small deviations of 0.001 inch or less!
The angle between the line of sight from test film holder to target and
the camera taking the photograph must be exactly 90 degrees to maintain
really square grid images.
With an optically flat piece of ground glass, the image is a perfect
square pattern. A 4x5inch film holder produces a bit of error (0.008
inches) at the
edges in one test case. A 6x9cm film holder has bulging errors reaching
0.010 inches near all the edges. The image is quite distorted. A sample 2
1/4 inch SLR back has a center bulge (circa 0.004 inches) and irregular
lines and bumps and hollows reaching 0.001 to 0.002 inches.
|
| Film Flatness Errors Table | |||||
|---|---|---|---|---|---|
| Format | 35mm | 2 1/4 SLR | 2 1/4 TLR | 6x9cm rollfilm* | 4x5 inch view** |
| frame to frame error (one roll) | +0.001/-0.001 | +0.001/-0.004 | +0.003/-0.001 | +0.015/-0.008 | +0.001/-0.008 |
| roll to roll error (one camera, thick to thin film) | +0.002/-0.002 | +0.000/-0.004 | +0.003/-0.001 | +0.015/-0.008 | +0.001/-0.008 |
| holder to holder error (one roll) | no test | +0.002/-0.004 | no test | +0.020/-0.008 | +0.001/-0.009 |
| worst error in system | +0.002/-0.002 | +0.002/-0.004 | +0.003/-0.002 | +0.020/-0.010 | +0.001/-0.009 |
| total frames tested | 32 | 48 | 24 | 24 | 16 |
Load the camera. Advance the film to the first frame. Set the shutter to B.
Trip the shutter with a cable release and lock it open (film is exposed
obviously). Look through the lens mount. Hold the camera so a centerpost
of a window, a pencil or similar dark straight object with a light
background is reflected onto the film.
A perfectly flat film should reflect a straight post or pencil image. If
you see any distortion, bulges, twists, or squigglies - you have a
real problem.
In Mr. Maersk-Moller's experience, nearly all the 2 1/4 inch SLRs and 60%
of the 35mm SLRS have noticeable film buckling.
By putting a thin glass plate at the film plane, flatness can be assured,
and lens performance improved (especially at wide open apertures). He
provides some figures for a Praktisix Zeiss Biometar f/2.8 which was
improved from unacceptable to excellent over most of its range. A thin
glass (microscope slide thick 0.01 to 0.03 inches thin glass) can be used
in place of his thicker installed plates for testing.
From: How to Flatten Your Film for Sharper Pictures by Hans
Maersk-Moller, Modern Photography, April 1970, pp.78-79, 120.
The key points here are that lots of cameras, particularly 6x6cm and most 35mm cameras, have visible film buckling. You can use his test to see if your camera does too. Whether you want to try his solution, at least you know now that the lens is not always to blame for wide open errors and softness - it may be your buckled film.
As Larry (Hemi4268) note:
Film flatness only comes into play with large f numbers. To get an idea of allowable film flatness in microns simply take the f-stop and square it.
TABLE THREE
f1= 1microns = 0.001 mm
f2= 4
= 0.004 mm
f4= 16 = 0.016
mm
f8= 64 = 0.064
mm
f16=256 = 0.256 mm
f32=1024 = 1.024 mm
f64=4096 or 4 mm
Table three is quite interesting if you accept
the usual values of 0.2mm for a combined error for both depth of focus
and film flatness. Basically, you run the risk of problems with film flatness
and focusing errors at or below f/16, per table three. Our calculated
table of depth of focus above provides more precise values based on
specified circles of confusion. But the point remains that at wide
apertures, the available depth of focus is surprisingly limited...
I'd suggest that individuals check film in their holders before becoming
panic stricken. My most ancient wooden holder maintains filn flatness
when tilted back, when vertical, and with small forward tilt. When held
face down (copy work), the bow which results is slightly less than 1 mm.
The questions are how significant that is, and how can one correct for it
- stopping down, or increasing extension by 0.5 mm (average deviation).
My observation suggests that I shouldn't worry about it unless the
camera is pointed down at a considerable angle, and then I might want to
tweak focus, and stop down to the f22-f/45 range.
The depth of focus is the tolerance for focus error at the film plane
which still results in acceptable sharpness. The following formula is
taken from the SPSE handbook:
Depth of focus (mm) = 2*C*N*(M+1)
where C is the circle of confusion required, N is the aperture and M is
the image magnification. For a subject at infinity, M can be set to
zero; greater magnifications (closer subjects) will give greater depth
of focus since the effective aperture is greater with extension
( Neff = N*(M+1) ).
The image resolution required on film, can be estimated by multiplying
the print magnification by the resolution (line per mm; lpmm) required
in the print. The inverse of that value approximates the circle of
confusion required.
The following tables assume a print resolution of 6 lpmm (4 is common
but not as critical), print magnifications which are reasonable for 4x5,
and a subject at infinity focus. The depth of focus formula used is
C*N(M+1) since only the movement of film away from the holder back is
considered.
Required circles of confusion:
Print mag 1 2 3 4 5 6
Print lpmm 6 6 6 6 6 6
Film lpmm 6 12 18 24 30 36
C mm 0.1667 0.0833 0.0556 0.0417 0.0333 0.0278
Depth of focus in mm for different apertures (N) and
print magnifications:
Print Magnification
N 1 2 3 4 5 6
------ ---------------------------------------------
11.3 3.771 1.886 1.257 0.943 0.754 0.629
16.0 5.333 2.667 1.778 1.333 1.067 0.889
22.6 7.542 3.771 2.514 1.886 1.508 1.257
32.0 10.667 5.333 3.556 2.667 2.133 1.778
45.3 15.085 7.542 5.028 3.771 3.017 2.514*
64.0 21.333 10.667 7.111 5.333* 4.267* 3.556*
90.5 30.170 15.085 10.057* 7.542* 6.034* 5.028*
* - indicates those effective apertures and print magnifications
which will very likely be limited by diffraction at the desired
print resolution of 6 lpmm.
The diffraction degradation is simply estimated by using Rayliegh's
approximation of the diffraction limit, 1600/f#, in lpmm. If the circle
of confusion required for a sharp print is less than that permitted by
diffraction, it's very likely that it won't be sharp. The effect of
film resolution isn't considered, since it is usually not a limiting
factor in LF photography.
Rayleigh Diffraction Limits
N lpmm Circle of Confusion
-----------------------------------------------
11.3 141.42 0.0071
16.0 100.00 0.0100
22.6 70.71 0.0141
32.0 50.00 0.0200
45.3 35.36 0.0283
64.0 25.00 0.0400
90.5 17.68 0.0566
Date: Tue, 08 Dec 1998
From: Dirk-Roger Schmitt Dirk-Roger.Schmitt@DLR.DE
Subject: [Rollei]Film Flatness, DOF
Concerning the recent discussion on the film flatness I would like to give
some more information:
The DOF in the plane of the film of a camera only depends on the aperture
of the lens.
You have to multiply the aperture, say 2.8, with the resolution limit also
used for the DOF calculation for the plane of the object. There are two
different limits (in Micrometers) common for 35 mm and 6x6, but I don't
have these values in mind now.
The value you obtain is in the range of about few 1/100 mm. It defines the
design limits for the tolerance of the camera manufacture and the film
nonflatness. This is the way Rollei designs the film channel. However, for
a lens aperture of 1.4 or 1.2 these tolerances are surprinsingly low when I
remember from my recent calculations on that theme. At that time I also
realized that the plane of the film tolerances of my two SL 35 E have been
out of any specs. (Due to the good quality control at the Singapore works)
Greetings
Dirk
Date: Sat, 27 Mar 1999
From: Jim Dunn jimmyd@dial.pipex.com
To: panorama-l@sci.monash.edu.au
Subject: RE: Fuji better than Linhof? Not!? Final thoughts?........... ArtPan
problem.
I was reading an article recently about a company that makes 6x9 cameras who
where unwilling to make a wider body because they could not get film plane
flatness to a level they where happy with ........ could this be something
to do with the difference between the Fuji and Linhof cameras???....... and
not the lenses.
I have an occasional recurring problem with my ArtPanorama..... the right
hand edge of the transparency ..... about 3 to 5cm in from the edge is
often soft, softish or very soft..... a recent film had a what appeared
to be a
double exposure of "only" this area..... Any ideas on what is causing it and
how to fix it............The ArtPan loads on the right and takes up on the
left.
Best wishes
Jimmy Dunn
Scottish Stock Photography
E-mail: jimmyd@dial.pipex.com
Date: Fri, 26 Mar 1999
From: "M. Denis Hill" denis@area360.com
To: panorama-l@sci.monash.edu.au
Subject: Re: ArtPan problem.
Jim Dunn wrote:
> I have an occasional recurring problem with my ArtPanorama..... the right hand > edge of the transparency ..... about 3 to 5cm in from the edge is often soft, > softish or very soft..... a recent film had a what appeared to be a double > exposure of "only" this area..... Any ideas on what is causing it and how to > fix it............The ArtPan loads on the right and takes up on the left.
This brings to mind a problem that had me stumped for a while with a V-Pan.
First frame would be fine, but subsequent frames were way out of focus on the
right side. I checked film guide roller height, groundglass/film insert
alignment, pressure plate springs, and other stuff I've forgotten.
I eventually determined that it was a pressure plate problem, evidently poor
finish (not smooth). The film was buckling on the take-up side due to drag.
My fix was to shim the pressure plate up .007" on the sides, allowing the
film to slip through a channel with less friction. In a later discussion
with another V-Pan owner, I learned that Chet Hanchette had started doing
the same thing on late production film inserts.
I've not, however, experienced this problem with my old-style Fuji, and
there is no comparison between the pressure plate finishes on the Fuji and
the V-Pan. In order to verify if it's the same problem, you'd have to
remove the lens and watch a roll of film as you crank it through.
Denis
Date: Fri, 26 Mar 1999
From: Dgling@aol.com
To: panorama-l@sci.monash.edu.au
Subject: 617s :: Fuji vs Linhof vs ArtPan vs ....
I have been reading a thread comparing various 617s.
It is not very fair to compare an old Fuji 617 with an recent Linhof 617 &
Super Angulon lens. Similarly, nor is it fair to compare a recent Fuji
617 &
EBC lens with an old Linhof & Angulon lens (if there is such a one).
The bottom line is in the optics. I have an ArtPan with a Large Format Fuji
EBC lens on it. It can be as sharp as today's Fuji 617 or Linhof 617. The
only difference is that this ArtPan costs much...much less than the other two
- body for body and especially lens for lens.
One thread mentioned his ArtPan's right side picture can be soft sometimes
- the feeding side; but I do not have this problem at all. Is there some
way to check for any mis-alignment, etc. Even a few 10th of 1 mm may
sufficient to cause some softness if one hold the circle of confusion to
be 1/10th of 1mm.
Date: Sat, 27 Mar 1999
From: YDegroot@aol.com
Subject: V-pan problems
It is probably better to make your own V-pan using a 5x7 camera to which you
attach a Navy-Torpedo or a Burke & James Royal panoram 6x17 rollfilm back.
I've heard that the V-pans are not as refined as they ought to be.
Again, film flatness is also determined by how well the film is "pulled" back
on the film supplying roll. There should be enough resistance.
Date: Sat, 27 Mar 1999
From: lawrence lawrence@hoflink.com
To: panorama-l@sci.monash.edu.au
Subject: Linhof and Fuji
The Linhof film plane is noted for its ability to achieve excellent
flatness. This is one of the many, many reasons I chose Linhof and
am exceedingly pleased with the phenomenal tack sharp images it
produces.
Lawrence
From: "Nicholas O. Lindan" nolindan@ix.netcom.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Improving Sharpness - PT Article
Date: Thu, 22 Apr 1999
Trmaj wrote:
> What I found out by spending about 12 hours measuring all my holders, > etc. with toothpicks, depth micrometer, etc. is that the film does > not rest exactly contiguous with the film holder bottom but floats > somewhat, so that a measurement made pressing the depth plunger firmly > against the film will push the film surface in several thousandths of > an inch, not where the film will be when you take a picture. I > finally rigged my measurement so that light shines on the surface of > the film at an angle and then let the plunger just barely touch the > surface of the film without pressing it in. In my case, there were > differences sometimes as much or more than 010".
Good advice. Very good advice. Needs repeating. So I have.
Nick Lindan
From: Jean-David Beyer jdbeyer@exit109.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Improving Sharpness - PT Article
Date: Thu, 22 Apr 1999
> > The quick toothpick test already has shown unacceptable variance between > > some of > > my holders. Drats! > > How many thousandths of an inch are people capable of focusing the > standard? I bet it isn't better than 20 thousandths - .02".
I think that is a very perceptive question.
Just as my light meter and shutters are far more accurate than my
decisions as to where to place a subject on the exposure scale (should
that shadow be on Zone III or Zone II?: a 50% error), so where I wish to
focus, most of the time. Since most of my subjects are not planar, I must
pick where I want the sharpest focus, diddle the camera movements and lens
aperture, and then hope for the best. So is 0.010" error that important? I
do not mean that it is not, exactly, but is my decision on where to focus
more accurate than that?
I have a Brown and Sharpe Mfg. Co. micrometer depth guage that is precise to
0.001" and easily estimated to 1/4 of that. Measuring cameras and film
holders
is not a rewarding experience. Even with new film holders and without film,
the depth of the "film plane" is not easy to measure since the plastic of the
film-holder is sloppy, so the depth varies across the surface of the
aperture.
Adding the film just makes it worse because of variations (from type to type)
in film thickness and film curvature (not too bad with Estar based films) and
the inherent design of the holder. Since I never got the standard on what the
depth should be, I measured the distance of the ground glass to the reference
edge on my Wisner T.F. This varied an easily measurable amount, too.
I think it is easy to get neurotic about these things. It is one thing to
say that I will use 200 l.p./mm film, the finest lenses, the highest
acutance developers, a tripod made from 8" steel I-beams anchored in
concrete for stability, etc., and then complain because the imprecision of
the location of the film emulsion, we are stuck with only 30 l.p./mm on
the processed film and only 7.5 l.p./mm in the final print. But do not
forget that the human eye is not much better (if at all) than that. Good
enough is good enough, provided we not get too lax in our definitions of
good enough.
When I work with 4x5, my focusing regrets have always been due to bad
judgement on my part, not on doubt as to the film location vis-a-vis the
film
plane defined by the lens and the subject.
rec.photo.equipment.large-format
From: fialkoff@aol.com (Fialkoff)
[1] Re: Improving Sharpness - PT Article
Date: Sun Apr 25 1999
>2) What is the normal manufacturing variability of the lens holders >themselves?
The answers to your questions can be found on Jon Grepstad's web site at
http://home.sol.no/~gjon/ in his FAQ on View Camera Construction in which he
states "The critical measurement (the distance from the film emulsion to
the surface of the film holder ) is 4.8 mm or O.190 inch. " and that " The
ANSI Standard for the depth of a standard 4X5 film holder is 0.197 +/_
0.007". When the film is loaded in the film holder, the depth is 0.190
inch " This should also be the dimension for the ground glass focusing
surface.
Date: Mon, 10 May 99
From: "David F. Stein" dfstein@ix.netcom.com
To: rmonagha@post.cis.smu.edu
Subject: Film Flatness Essay
Bob,
Great job. Not an easy read, but an important one. All these arguments
on lenses when cameras are never really checked for accuarte focus;
assuming WE can focus.
But with large format I think it's worse. The film holder is like the
windshield wiper of the car-ancient technology compared to the rest:
turbo engine, ABS, traction control, electronic ignition,
computer-controlled, flash ROM, dual cam overhead engines, etc. and we
have this flimsy piece of rubber, barely attached to a clumsy blade,
waving around by a simple motor! Thousands of dollars for cameras, the
finest lenses in the world, the most sophisticated emulsions in the hx of
photography-and the film can flop around in a holder, whose plane
location we don't even really know.
Sincerely,
David Stein
From: "Rick Rieger" rrieger@compuserve.com
Subject: Re: Bronica GS-1, Mamiya 7
Date: Wed, 19 May 1999
I'll second what John Sparks said. I also have a GS-1. Like John, a
friend has a Mamiya 6 (not 7). I don't see much difference in the results,
but there have been no real A-B tests that we have run. I believe most
professional quality medium format systems will offer the user very fine
results. It gets down to what features and costs fit your needs.
The photo writer Ctein has stated that, in his opinion, medium format film
flatness and tolerances in the film backs are more important to image
sharpness than the lenses.
I have a Fuji 6x9 rangefinder, which also gives me superb results.
However, the Bronica SLR is a lot more versitile camera.
Rick Rieger
Date: Thu, 29 Apr 1999
From: Evan Ludeman ludeman@bit-net.com
Subject: [KOML] Whither the film plane?
Flipping through my recently acquired tech manual (thanks Doug) I
encountered a bit of a surprise. Avid readers of the list may recall my
mutterings, musings and ramblings about K-O focusing, rangefinders, etc.
and will not be surprised that this is the first part of the manual I
looked at. The surprise concerns the location of the real image plane vs.
the film "aperture" (in K-O manual speak). Evidently, the K-O was set up
at the factory to focus the image 0.2mm (0.008") in front of the film
aperture (i.e. rails), "to account for the characteristics of roll film".
Huh? The implication here is that the designer is assuming that the film
will bow out towards the lens. The manual also notes that the K-O ground
glass attachment incorporates this 0.2mm offset into its construction (can
anyone confirm this?).
Q: Is this reasonable, necessary or advisable? Is this typical of roll
film camera design?
N.B. 0.008" is actually quite a lot in terms of D.O.F., about 1/2 at f3.5,
and 1/4 at f8. More, if one uses a more critical circle of confusion than
the K-O 0.058mm manual value.
I have my camera adjusted to put the image plane in the plane of the film
aperture. It seems to work very well this way although I have not done any
rigorous wide open aperture testing on film -- in normal use I rarely open
up past f8.
regards,
Evan Ludeman
From: dickburk@ix.netcom.com (Richard Knoppow)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Improving Sharpness - PT Article
Date: Wed, 21 Apr 1999
"Nicholas O. Lindan" nolindan@ix.netcom.com wrote:
>"Jeanette D. Walton" wrote: >> >> From Jack: >> Re the article in May/June PT "Improving View Camera Sharpness", (nice >> photographs btw Mr. East), but why not use a caliper instead of a >> toothpick? Sears sells a "Student Grade" caliper which measures depth >> to 0.001" for about $12, and it is acurate for this purpose -- which is >> measuring the relative distances of the gg screen and the film plane. >> >> Seems easier since you don't have to remove the back. > >Yeah, Sears does, and wow is it an explicative in need of deletion. I >got one, thinking it would be a good thing to keep the in automotive >tool chest in the garage. I returned it, claiming it was only good for >repotting daisies. > >Buy a good vernier caliper - buy it used if you like. Every one should >have a good set of calipers: Browne & Sharpe, Mitutoyo etc. They don't >go bad. They last forever. > >Sears sells Mitutoyos under it's Craftsman sticker but most of their >stores don't carry precision measuring equipment anymore. > >A quick search on ebay says a decent one should be obtainable for $20. >Look at http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=92917234 >Search for 'vernier calipers' 'vernier dial calipers'. Someone is >selling what appear to be OK chinese ones for $12 to $16. > >But what is really needed for this job is a depth micrometer. >I'll be damned: >http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=91521752 > >Oh dear, I am a real lover of precision tools. I have to stay away from >this stuff. > > Nick Lindan
I use a depth micrometer I bought at the hardware store for about
$33 US. Its good enough for checking film holders.
You need to make a reference surface to measure from. A piece of
sheet aluminum or plate glass is suitable. It needs to have holes
drilled in it to clear the feeler of the micrometer. Measure with film
in place.
To arrive at a standard depth you can measure the depth from the
reference surface of the back (the part that locates the front of the
holder) to the ground glass surface. The depth from the front of the
holder to the film surface shold be the same. You should measure the
holder with film in it, both because of the thickness fo the film and
to check for buckling.
Old holders, especially large wooden ones, are likely to have warped.
I have several old 8x10 holders, and some 4x5's where the center plate
of the holder has shifted so that the depth is too deep on one side
and too shallow on the other.
---
Richard Knoppow
Los Angeles, Ca.
dickburk@ix.netcom.com
From: jimkphoto@aol.com (Jimkphoto)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Improving Sharpness - PT Article
Date: 21 Apr 1999
Hello everyone,
I tried both the tooth pick method and the depth micrometer method
yesterday on all of my film holders and I too found differences in each
reading. Its true, the film does seem to "float" a few thousaths of an
inch on some of my film holders.
I personaly have not had much of a problem with focusing and have
checked my film holders in the past with the depth micrometer. the tooth
pick method is a good cheap way to get a measurement as long as you are
careful in keeping your ruler, or straight edge level. Perhaps placing a
tooth pick on both sides of your straight edge would be a little more
helpful.
Above all else I thought it was a good article and I agree with everyone
that that there is nothing better than a good quality tool to do the job
right.
Jim
From: B Peters bill.peters@home.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Improving Sharpness - PT Article
Date: Thu, 22 Apr 1999
Erik,
To answer this question for myself I set up my Wista VX with 150mm f5.6
lens and a 0.001 inch dial test indicator on the front standard. I did a
run of 20 focus measurements, throwing the camera well out of focus each
time and then focusing on a test target using an 8x Nikon loupe. (I did a
preliminary run of ten measurements and adopted the mean as the zero
position.)
My maximum errors were -0.006 and +0.005. My mean error was -0.0013.
In summary, most of the time it is possible to focus will within ANSI
tolerance for film holder error.
In note that it is harder to be so consistent and close on slower lenses. I
have greater difficulty focusing my 255 mm f10 lens or my f8 wide angles.
Still, I get very sharp prints from all these lenses.
Bill Peters
From: Tom Haller eckert.haller@worldnet.att.net (Tom Haller)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Improving Sharpness - PT Article
Date: Fri, 23 Apr 1999
This article caught my attention too, not because of any abstract
concern with precision, but because I've notice too often that my 4x5
enlargements don't seem perfectly focussed. I measured my holders vs.
the groundglass and found (1) in 6 holders there was some variation
with one being way off and (2) the film in an average holder was
definitely further from the lens than the groundglass. I solved this
problem by cutting a shim out of heavy black paper for my Wista DXII.
By the way, my variation was to tape a dark slide to the ruler instead
of a toothpick. Because of the slightly concave leading edge of the
dark slide, I have two corners touching down -- like your
two-toothpick idea. My test to see if a holder was roughly within
tolerance was to check if I could pass a piece of film between either
corner of the slide and the film in the holder, or between the ruler
and the front of the camera back in the two places it should have been
resting.
....
From: Linda A Whatley linda_aw@ix.netcom.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Improving Sharpness - PT Article
Date: Fri, 23 Apr 1999
>From Jack >I promise to buy a better micrometer and not rely on my cheapo sears model >(an interesting way to start a thread.)
.. . .
You can buy very good imported calipers nowadays. I use one from the Grizzly
machine tool catalog-- about $20, stainless steel, with a .001" vernier, very
well made in China (not the stamped-out ones you sometimes see). You can
also
get the dial model for about $25. Other catalogs have them, but I haven't
seen them in hardware stores that carry the traditional brands.
- Larry Whatley
From: Jon Grepstad gjon@online.no
Newsgroups: rec.photo.equipment.large-format
Subject: Re: film plane tolerance for focus
Date: Tue, 27 Apr 1999
....
The ANSI standard T dimension for 5 x 7 film holders is 0.228" plus
minus 0.010. The T dimension is the "depth" of the film holder when film
is not loaded.
Jon Grepstad
From: reynolds@panix.com (Brian Reynolds)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Improving Sharpness - PT Article
Date: 27 Apr 1999
Nicholas O. Lindan nolindan@ix.netcom.com wrote:
>I covet a set of Sinar precision film holders. > >I have contemplated that it shouldn't be too hard to make single-sided >vacuum holders from plane-jane Fidelity holders. Has anybody tried >this?
You might want to check out
--
Date: Fri, 4 Jun 1999
Hi Phil and our Rollei lovers,
Film flatness is absolutely one of important factors to ensure imagine we
took from our lens will be as what we expected. The other one might be the
flatness when we enlarging the negatives.
As most of our groups, just as me, might be still have to hand-wind the film
after we shoot. One of my friends told me that one of the benefits to keep
film flat is that after we shoot for the film, do NOT WIND the film until
you are going to shoot next one. It might incur some inconveninet.
Especially when you say "C" to someone (Sorry, I have to wind the film).
However, film should be able to get more tension (flatness) after we wind
it. Manual might be complicated. But, it will last loooong looong. Only if
you love it.
Your Rollei 2.8D and Zeiss Ikon clone
Best Regards,
Ming-Sung Lin
Date: Mon, 14 Jun 1999
All I have are the older single-latch backs, but all are in extremely good
to excellent condition. So far, I've seen no *apparent* signs of a film
flatness problem, and all backs function perfectly!
Since the film will take a set curl where it wraps around the rollers if
left loaded, I've loaded up some Velvia and shot a few frames.Then after it
had been left loaded several days I shot again to see if the next two frames
or so had any apparent flatness problems from being left curled tightly
around those tiny rollers. No visible signs of any problems were apparent on
any of the frames when inspected with a loupe, so I haven't worried about it
since.
Bill
Date: Wed, 22 Sep 1999
Hello,
While adjusting the mirror for focusing alignment between film plane and
focusing screen, i have made following experiences (2003fcw with 2/110,
standard Accute-Matte screen):
1. The position of the film plane for my two backs is not identical. The
difference is about 1/2 of DOF at F2.
2. The film plane position in the same back is pretty consistent and better
than I was expecting (1/4 of DOF worst-case from about four film rolls)
3. The average focus setting is different when observing the screen with
waist-level finder or PME-3 prism. While using the finder with higher
magnification, the focus setting is more consistent. But the average
values for
finder and prism are different, the difference is again about 1/2 of DOF.
4. The accute-matte screen gives subjectively a larger DOF than the film
shows.
This makes the focussing less accurate.
That means that: either two matching backs have to be found and used with
a screen with focussing aids (microprism and/or split image, or is the
accute-matte-d screen more accurate to focus?) or the mirror wil be
adjusted for one back and one finder (a take-it-easy solution).
Not that my photography is that much demanding. I just made my first test
shots and found those made at F2 to be out-of-focus. As I like having my
tools properly set (makes more fun to use), I started this evaluation. As
I am new to MF, I would appreciate your opinion. Is the 2/110 lens that
kind of difficult to focus? There was a posting by Kornelius J. Fleischer
some time ago describing focus-bracketing for getting the maximum lens
resolution. Is this the universal solution?
Sorry for this very technical posting.
Friendly Regards,
From Rollei User Group List:
Mark,
Your photographer friends are right that the Contax 80mm/F2 is not exactly
stellar wide open. But did they tell you how good the lens is stopped down?
It's breath taking at f5.6!
The 80/F2 is the fastest std lens in medium format. It has a very shallow
DOF, so any focus or film flatness imperfection will show clearly. But that
doesn't mean the Contax has worse AF or film flatness than anyone else;
these imperfections are inherent in any medium format AF SLR, it's just that
the imperfections get amplifed to a greater degree with Contax's faster
lens. And the Contax shouldn't deserve to be penalized for having a faster
lens, should it?
(It's obvious that the Pentax should be sharper wide open--it's one full
stop slower! But try the Contax and Pentax at same aperture then the
conclusion is not the same. p.s. I had a Pentax 645N before it was stolen.
My Contax is an insurance replacement...)
In fact, the Contax addresses film flatness and AF accuracy better than
anything else out there. To counter film curvature, the Contax has an
optional vacuum insert that keeps film flat on the pressure plate during
exposure. To increase AF precision and accuracy, the Contax uses a 1/5"
250,000-pixel sensor. This kind of precision is unheard of. (The Multi-CAM
1300 AF module in the Nikon F5 and F100 has, well, 1300 pixels.)
In this view, the Contax actually has the most advanced AF systems on the
market. Unfortunately most people are quick regard the Contax as what a slow
35mm SLR would be, instead of looking at it as the fastest medium format SLR
available.
Regards,
Chris
From: hrphoto@aol.com (HRphoto)
which is the very reason why some camera manufacturers, like Leica, use
tolerances of 1/100 mm (1/2540 inch) for the lens mount alignment and lens
to film plane distance.
Heinz
Newsgroups: rec.photo.equipment.35mm
Robert Monaghan wrote:
Two remarks. First, according to Contax (RTS3 brochure), the film flatness
error measured for top-of-the-line SLR's amounts up to to 0.03 mm. Second,
according to my calculations the depth of focus of a typical 50mm lens at
f/8 is 0.24 mm, and 0.12 mm at f/4. (CoC = 0.03 mm & lens at infinity,
although depth of focus does not depend much on focal length and subject
distance, contrary to depth of field.)
Who's making a mistake?
Regards,
From: Roland roland.rashleigh-berry@virgin.net
....
Thanks for that. I think people should be made more aware of this
problem. I am certainly aware of it. I tend to stop down to f8 for all
my outdoor shots (with a standard 50mm lens) because of this problem.
When I am using a manual camera I make damn sure I wind back the film to
take up the slack. F8 is my "standard" f-stop because I know the
depth-of-field is sufficient to hide this problem. I only go for larger
apertures if I have need of a specific depth of field effect or if I am
using a wide-angle lens and need more light.
Roland
From: Anders Svensson Anders.-.Eivor.Svensson@swipnet.se
....
Some points:
The film's ability to keep as flat as possible is also important. The
inner layers of the film cartridge are much worse in this respect as they
are more tightly wound. The opposite may be true in the other end, so
expect (perhaps) that equilibrium (in this sense) to be in the middle...
The idea that tightening up the film rewind crank to get flatter film may
or may not work. I would advice against it, as the film could be unevenly
stretched.
A large camera, with a long "lead in" and a long "lead out" before the the
film exposure opening (shutter area) is also (probably) beneficial to film
flatness. Letting the film rest (even for a short while) after winding may
also help.
Newer motor winded cameras wind after shooting, but with old manual
cameras, the advice has always been to not wind, as the camera will be
better off with a slack shutter. Perhaps it is bad advice for film
flatness.
These are discussion points, not facts.
--
From Rollei Mailing List:
ShadCat11 wrote: the Rollei negs alternated one sharp, one out of focus,
although I didn't touch the focussing knob between exposures.
There's a lot on film flatness issues (which sounds like your problem)
at this site: http://www.smu.edu/~rmonagha/mf/flat.html
I recall discussion on not winding too fast between frames with a
Rollei, as it strains the film, and perhaps bows it slightly. You might
find more in the archives. I have a 3.5F Planar myself, and with fine
grain film on a tripod, it's the best I've seen. (Of course, I haven't
tried everything. :+)
Bill Maxwell, who has spent a lot of time with Rolleis and an auto
collimator, says the film is bowed, and he takes an average for his
focus adjustments. With some makes, the pressure plate springs fatigue
with age. I haven't heard that with Rolleis, but anything can happen.
Remember, it's "f/8 and be there!" Although f/11 might be better,
in this instance.
Phil Stiles NH USA
From: frostycat@my-deja.com
I agree with everything Michael says here. Perhaps I should have added:
Focusing aids I use are Spectra Astro-systems SureSharp which he
mentions or the Takahashi microscope and ground-glass system. With the
Tak system you open the shutter and place a piece of frosted glass
right on the rails in place of the film. Focus a star through the lens
onto the frost which is exactly where film emulsion will be. Place 60x
microscope on the glass and focus the instrument to achieve smallest
possible star-dot. When I did this for the first time was astonished
to find how inadequate/inaccurate my camera's viewfinder was. More
interesting was that I had considered my previous photos pretty darned
good when, as is obvious to me now, they actually weren't even in-focus.
Also, be certain to let everything cool down completely before you do
it. Expansion/contraction in body and instrument of longer focal
lengths will affect focal distance.
Of course after that shutter-shake can still be a problem but precise
focus is much easier to obtain.
Actually, they're both a pain. However, if you want good photos you
have to handle it.
Michael Richmann richmann@concentric.net wrote:
From Rollei Mailing List:
When you say "out of focus" are you saying that there is no focus
anywhere?
If the film has bulged in or out a little it will reveal itself by showing
focus in the wrong position, far or near. Does your image lend itself to
revealing this?
It is hard to imagine the film being able to bulge totally out of focus in
such a time-proven, high quality film path as a Rollei. A 75mm lens
focused at 20', set at f5.6 using a CoC of .0022" yields a depth of focus
of about .025", easily deep enough for typical 120 film flatness errors.
Both myself and a friend who is an architectural photography specialist
have had 120 film flatness problems that were great enough to create
curved lines on film (no barrel distortion) but still well enough within
the depth-of-focus range to provide critically sharp prints.
Is your image totally without focus anywhere? It might suggest a wiggling
tripod from a nearby heavy-footed photographer (although camera-motion
softness is usually tell-tale) or, perhaps, something is loose in the lens
and flopping back and forth.
Mysterious.
Tim Ellestad
From: hemi4268@aol.com (Hemi4268)
Hi
Actually there is no technical reason in lens design that would allow you
to see the difference. What's it really happening has to do with the body
design.
Most SLR bodies, Nikon included have mirror errors better then 10 microns
and some can be as much as 50 microns.
The Leica bodies are built to a much closer spec of under 10 microns.
The rule of thumb in how much focus error you can have to f stop is:
So you see, if your SLR camera has 50 microns of error (about 25% of all
SLR's have this much error) then you must be stopped down to about f5.6 to
back out all the focus errors.
With a Leica camera, you don't have to do this. The 1.2 lens on a Leica is
correctly focused even at 1.2 vs the Nikon which has to be stopped down to
maybe f4.
Larry
From: hemi4268@aol.com (Hemi4268)
Hi
Yes very good point. Film flatness is an issue. Although, most film wave
are under 10 microns. A f-stop of f3 or better will usually correct these
issues. It's the mirrors that are over 25 microns that cause all the
problems.
Take 30 2nd year photo students at a major photography school. Test each
SLR mirror. You will find this
These represent all camera brands that most people wanting to be
professionals
might buy.
You can have the sharpest lens in the world but if your camera is not
right,
your pissing in the wind.
Larry
Date: Sun, 9 Jan 2000
1. Don't store your film curled up.
2. Reverse the curl of the film for one day with the emulsion on the
outside.
The reverse curl works well with transparency film that I use to mount
into stereo frames.
From Rollei Mailing List:
If you have the time, Bill Maxwell will give you a long and interesting
dissertation on why focus on a Rollei TLR is NOT properly set at the
plane of the film rails but at a point slightly closer to the lens (to
accommodate typical film unflatness, as I recall,) and why you need a
fiendishly complicated device (which I still can't picture) to do it
properly. At least, that's what he said he was doing to my 2.8F when he
worked on it earlier this year.
Cheers,
Bob Shell wrote:
....
From Leica Mailing List:
There is a 35mm camera (the Contax RTS III) with a vacuum back designed
specifically to keep the film flat. There either is, or will be, a
medium-format camera that has a vacuum back to keep the film flat (one
is promised for the Contax 645, which is selling like hotcakes BTW,
and--much to Contax's surprise--doing better in the USA than in home
market [which for Contax is Japan]). I don't know whether this is
actually available yet and I'm too lazy to go check.
Film flatness is indeed a valid technical concern for specialist
photographers. It's just not of much practical concern to photographers
for pictorial photography--except sometimes when a frame with a "memory"
of a "set" curl creates obvious unsharpness in a negative--and sometimes
in large format. Which is why you don't see much effort to correct the
"problem" in the products on offer (Contax excepted, and I have a
feeling this has something to do with the fact that Kornelius Fleischer,
head of 35mm optics at Zeiss, is an aficionado of high-resolution
photography! He uses surveying tripods and has access to the legendary
Zeiss S-Planar process lenses for enlarging, lucky dog!)
The Contax vacuum backs were based on the technology used for 10x10
aerial reconnaissance and satellite photography.
You think medium format is bad, try large format. It's been demonstrated
that the film not only does not lie flat, it can _move_ during
exposures. This can occur because of "sagging" or because of the film
suddenly being exposed to ambient humidity when the darkslide is pulled.
At any rate, measured with a micrometer, 4x5 film lies very far from
flat in a holder. In fact it resembles a rumply blanket.
At least one of our contributors uses a special vacuum 4x5 back, and
another has devised a system whereby he uses five little patches of
double-stick tape on the inside of his 4x5 holder--he carefully loads
the film and then presses it lightly with his fingertips to make the
tape "engage" with the base side of the film. He then uses these holders
for very long exposures, so his film won't move or sag during the
exposure.
- --Mike
From: w.j.markerink@a1.nl (Willem-Jan Markerink)
"Mike" NEDSNAKE@email.msn.com wrote:
I have seen a large article on this subject before, it's the difference
between viewfinder focus (mirror) and film focus, caused by crappy film
pressure systems....see my homepage for a copy of that article:
http://www.a1.nl/phomepag/markerink/mf_focus.htm
From Leica Mailing List:
Austin Franklin wrote:
I have been shooting MF and LF for a while, and film flatness is
definitely an issue for me. If I've left film in a Hasselblad back for a
day or more,
I won't shoot on the next frame, as the center will be focussed on more
distant objects than the edges (I've seen this a number of times).
Similarly on Mamiya 645 backs, Graflex 6x whatever backs for 4x5, Horseman
6x12 and others of the same transport design. Also Noblex 150 series.
Calumet C2 backs and Sinar Vario backs don't have this problem, and I can
use every frame, but the C2 back is never consistent, and obviously has
some other problems. The Mamiya 6 seems to have the best film flatness (or
best matched to lenses) of any MF camera I use. In 4x5, vacuum backs are
used for exacting copy work for a very good reason. Point the camera down,
and the film sags. Fortunately, for most of my work the emphasis is on
keeping 4x5 film dead vertical. Shooting at f/11 to f/32 also helps. In
8x10, I've had the film fall out of the holder in the camera when taking
shots looking down when shooting from equipment that vibrated every few
minutes! Talk about film sag!
Soooo... In MF, with most cameras I try to finish the roll fairly
expeditiously, and wind on the last frame or two rather than save it for
the next day. I'll take shots on the Mamiya 6 with film that has been left
in the camera, but if critical and at wide openings, I'll still wind on to
the next frame. The Sinar Vario back I don't have anymore - good riddance!
As for "The Hasselblad Manual" (mine is the second edition), Wildi does
not necessarily seem like the type of author that would bring up a subject
like film flatness. As in many books of this type, and this certainly
includes many about Leica, it is more an extended instruction manual that
doesn't probe a systems weaknesses.
From Leica Mailing List;
Mike Quinn wrote:
The model I use that seems to explain and predict film flatness well,
according to my resolution tests and experience shooting Rolleis and
others for 20 years, is that is that the film "remembers" the curves it
goes through prior to getting to the film plane. The tighter the curve
and the longer it has sat there, the more it will remember it. Likewise,
the longer it sits on the film plane, the more likely it will "forget" the
past curves -- some say "relax." Film thickness, type, and even humidity
also affect the problem.
For evenness on a medium format (MF) camera, it appears that the
uniformity of the film's tendency to curl is a critical factor. If the
film has been sitting for a while and is then wound to the next frame and
shot immediately, it will have part of the frame "remembering" the curl of
the roller. That will throw the frame off the film plane by differing
amounts depending on lots of factors, including the extent of the past
curl. The worst I ever saw in real world shooting was when I shot an
English cathedral steeple with my Rollei SL66 on a very cold morning.
The frame that had sat on the reverse curl put an out-of-focus line across
the frame (and steeple) that was visible without a loupe.
When I'm testing a lens -- usually with Tmax 100 or Agfapan 25 (but this
works with most films and MF cameras) -- and I want to be sure that the
film is flat, I simply waste the frame that has been on the roller. So, I
shoot a blank, immediately go to the next frame, wait 2 minutes for the
film to "relax"/"forget" its momentary stay on the roller, and shoot. I
don't think I've ever seen this procedure fail with the films I use --
with one exception. Tech Pan in high humidity is so hard to control that
I've abandoned it for MF shooting. The emulsion appears to swell, and the
film base has so little strength to offset this, that it will randomly
come off the film plane with every procedure I've used -- the "reverse
curl" back of the SL66 being worse than the TLR or rangefinder type
cameras I've used.
In the real world, when I'm shooting MF I simple keep track of how long
the film has sat on the roller. When shooting a series of shots fairly
quickly, the issue can be almost ignored. When I do landscapes, want
maximum sharpness, and the film generally sits still for some time while I
hike to a different location, I end up shooting every other frame.
One person on this thread asked about the Fuji GA645. I have one, and it
has the least problems with film flatness that I've experienced with an MF
camera. (The older GS645 was not as good.) On the GA645 Zi Fuji put two
rollers on the face of the film just outside the frame that hold the film
on the pressure plate. It appears to work well. I've found I can shoot
it like a 35, virtually ignoring the film flatness problems that are
usually associated with MF shooting. (Moreover, that Fuji zoom is, in
some ways, better than my Zeiss glass -- amazing.)
Paul Roark
From Leica Mailing List:
When you want to do the disposing, send it to me.
This one I haven't used, but I thoguht it only holds one sheet of film.
Could be wrong; I only saw it once at Photokina.
Sinar also sells adhesive film holders for 5x7 and 8x10 for $350US approx.
I used to do it with $25 Lisco's and some low tack adhesives.
BTW, the Vario back I had is now up to version II, at a price of $2893US
from B&H. Considering that I paid (only) $2000Cdn for the version I that I
had when it first came out about 15 years ago, that doesn't seem so bad,
since the one I had never worked properly. :-( Film stayed flat, but
spacing was 'something new every day'. Sometimes I only got one shot per
film, if I just kept winding. In comparison, my 6x12 Horseman back does a
good job as long as you don't wait a couple of hours between shots, 'cause
then the film ain't flat.
With respect to: what format?, use what works. More specifically, use the
most suitable thing that's available to you. If I don't have my Sinars
with me, I don't tend to take good pictures with them, and even lousy ones
are scarce. If I have my Noblex with me, I often take panoramic pictures.
If my Mamiya 6 is at my side, I take MF pictures. I see differently, and I
take different pictures. Not better; not worse. Different.
I find it quite difficult to take good photos with different formats on
the same job, or even different film types. One format or one film type
usually dominates my view. If I'm seeing properly in B&W on 4x5, the color
shots tend to be just colorized B&W shots, not good color shots.
Similarly, if I have to take 35mm slides on the same job, the shots tend
to be just too small, colorized 4x5 B&W shots. Some days I can do a decent
jobs on a couple of different setups, but many days it doesn't come off
properly. I think this is an extrapolation of the 'one film, one camera,
one lens' concept.
On this same note, if I use a Leica M to do the 35mm stuff, it tends to be
more 'true to 35mm color slides' than if I use an SLR. Might be because
the rangefinder M is _SO_ different than 4x5, whereas the SLR is closer to
4x5 viewing and I tend to use the same mindset more easily. Any of you
other multi-format/multi-film shooters have similar experiences?
From Leica Mailing List:
Regarding "Film Flatness":
It would appear that the people at Franke &
Heidecke in Braunschweig encountered the problem of "film flatness" quite
a long time ago in their engineering of the Rollei cameras. At least two
models of their 2¼" square format reflex cameras [I owned a Rollei flex F
and also a Tele-Rolleiflex with this feature] offered optical flat glass
plates located in the image plane, ahead of the film, to offset the
tendency of the 120 film to "bow" or "buckle-out" in it's location in the
aperture of the image-making portion of the cameras. It appears that the
pressure plate by itself in a single plane did not correct the geometry of
the film in this critical area. It is reasonable that the film would
present a very flat surface to the image with this feature. I do not know
that Hasselblad ever offered such a feature although it is certainly
reasonable to assume that their engineers would aware of this design?
Bill Carson,
KE7GM@earthlink.net
From Leica Mailing List:
On Sun, 19 Mar 2000 Austin Franklin wrote in part:
Perhaps you could share the resolution tests that showed this [film
flatness problem] phenomenon
with us?
Here is a series I recorded for a Rollei F. I'd heard that the film
flatness of this design was better than the SL66 -- and I believe it is,
though my SL66 tests are too long ago for me to find. The Rollei (3.5)
was shot at f11, which is what I generally use for landscapes and tripod
shooting.
Film (Agfapan 25) wound to frame 1 and left for 14 hours: center
resolution 85 lp/mm, edge 40.
Film wound to frame 2 and left to "relax" 20 minutes: center 50, edge 40.
Film wound to frame 3 and left to relax 4 minutes: center 65, edge 38.
...
Film left on frame 6 for 2 hours.
Film wound to frame 7 and left to relax 5 minutes: center 36, edge 48.
Note that when I have tested MF cameras in shooting quick series of shots,
there is no problem with film flatness. As such, a person shooting a
wedding or some event where the film is not going to sit for a while
really doesn't need to worry about this. Also, once the resolution is
above 50, it's not likely to be noticed much in most instances. However,
the ability to enlarge the center section of a frame would certainly be
affected. Moreover, in my landscape shooting, the film often sits for an
hour or more.
My resolution tests on Tmax 100, using the same test conditions:
SL66 Planar HFT at f11: center 75, edge 69; Zi at 90: center 80, edge 60.
SL66 Distagon 50 at f11: center 90, edge 42; Zi at 55: center 90, edge 70.
These results are really not that surprising. The newest high end, low
ratio zooms are getting very good, especially at the wide end. On the
other hand, retrofocus wide angles are usually second rate. Note,
however, that the floating element 50 for the Hasselblad could well be the
best of the bunch. Sadly, it is not available for the SL66.
________________
I did an interesting but largely irrelevant test of the 150 Sonnar on 35
mm. I adapted a bellows to be a mount for my SL66 lenses to fit onto a
Canon FD, complete with tilts, etc. The test I remember, because it was
rather amazing, was with the 150 Sonnar at f 4. It produced 100 lp/mm
center and "edge" -- a performance that was considerably better than any
lens I'd tested. However, the test is not "fair" or comparable to a 35 mm
lens because I was able to focus the 150 on both the center and edge that
I measured due to the tilt capability of the mount. I didn't measure the
other edge, and I assume it was terrible. The vast majority of lenses
I've tested show some degree of curvature of field that decreases edge
sharpness in a normal test where the film plane and target are parallel
and one focuses on the center.
Paul Roark
Date: Tue, 02 Nov 1999
from: flexaret@sprynet.com (Sam Sherman) 11-2-99
Bob,
That is a good series of articles and info, I have downloaded it for
further study.
My Bronica Deluxe has some of the best film flatness.
Remember it has the flatness bar which comes down.
My Bronica C is very flat and the S-2 and S-2A pretty good with the
improved one roller insert.
I am getting sharp pictures with all of these, but they can all be
improved.
I am always interested in the sharpest max. center sharpness and let the
edges take a walk.
The new Hasselblad back and others seen by me at the NYC Expo have a
slotted pin not just round like Bronica S2-A which fits into the full 120
spool. They have some spring tension on this to create drag and tighten up
the film against the pressure plate.
I think this is a big joke which will wear out the wind gears quicker.
I tried such an idea on the insert for Bronica S-2 and it did next to
nothing and I prefer not to damage the gears.
Hasselblad is high precision, nicely made and machined, but still so
primative.
Nothing new there for film flatness. How can they claim their 100MM f2
lens is sharp wide open?
- Sam
----------
From Leica Mailing List:
Some years ago I was looking for a medium format camera for landscape
work. I part traded an M2 for a Hassleblad. Many times I'd leave the film
in the camera for some hours or even days between shots. Under these
conditions the lack of film flatness was a serious issue and certainly
showed on the final prints, especially with slow fine grained films. If
you looked at the reflection of light on the film after winding on you
could clearly see the bump where the film had been bent round the roller
in the magazine insert. After returning the magazine twice to the
importers I gave up trying to get the problem fixed. One year later I
traded the Hassleblad.
Later I returned to medium format with a used Rollei SL66. This also had
similar problems caused by an abrupt bend in the film path. However, it
was the tilting lens panel which sold me on this camera and is the reason
I still use it for landscape work. Ironically this feature can cause film
flatness to be even more if an issue. The tilting panel can give infinite
depth of field, making near-far sharpness possible at full aperture but
the depth of focus at the film plane is very small under these conditions.
I know Rollei recognised the problem and later SL66 magazines were fitted
with a larger diameter roller. To minimise unsharpness I don't use the
next shot if the camera hasn't been used for more than 15mins and after
loading don't wind to the first frame until I'm ready to use the camera.
One camera I've found to have no apparent problems no matter how long the
film is left in the camera (within reason
Bob Parsons.
From Leica Mailing List:
William Carson wrote:
Yes, Hasselblad has offered such a thing, in the form of a Reseau plate in
their MK70 and MKW cameras. These are their photogrammetric models for use
with special versions of the Biogons of 38 and 60mm focal length and of
the 100 Planar. This plate (a calibrated piece of glass ahead of the film
plane) serves two purposes; one, to hold the film perfectly flat and two,
it is etched with fine crosses to allow the negs and prints to be
measured. When you buy one of these cameras, you get a detailed report on
the geometry of the whole camera, including an exact report on the
distortion remaining in the lenses and the remaining curvature in the
film. Film used is not 120, but 70mm because it can be held more precisely
than 120 film. Among other things, these cameras are used in my field,
architecture, to allow production of as-built drawings of older buildings
which might otherwise be hard to measure.
From Leica Mailing List:
Not only Hasselblad - also Rollei had similar glass plate for the f:2.8
Rolleiflex models and also the Rollei 35 metric had it.
All the best!
Raimo
From Rollei Mailing List:
Recently there was a discussion about removing the plane glass plate
from the focal plane of a 'flex as well as a thread on planar image
quality. So I have the following questions.
-1- I understand that the plane glass kit was introduced to enhance
film flatness. But it is well-know in classical optics that a plane
glass not only shifts the image by about 1/3 (for a refractive index
n=1,5) of its thickness (easily corrected by changing the film
pressing plate position) but also re-introduces a certain amount of
spherical aberration. Microscope lenses used in biology are designed
to view through a .18mm standard glass plate and pre-corrected to
cancel this spherical aberration. So my question is : did people try
a side-by side comparison of image sharpness with and without the
plane glass kit?
-2- The answer might be that film buckling and de-focusing being the
main effect, the benefits of forced flatness overcome the
(theoretical) optical aberration generated by the plane glass.
However if so, why did Rollei stop shipping the plane glass kit as a
standard item in the last 'flex series?
-3- for people who have used the plane glass kit routinely, how about
cleanliness issues i.e. about dust sticking on the plane glass and
potentially scratching the film?
--
From Rollei Mailing List:
I'm not sure about pressure plates for Tech Pan but there is a special
pressure plate for 72 frame rolls of film. The film is thinner. This is
from my 3003 manual. I have never seen a 72 frame roll of film. I hav'nt
looked hard either. Perhaps only Tech Pan is available in this
format. Anyway that's my $.02.
Carter
From Bronica Mailing List:
from: flexaret@sprynet.com (Sam Sherman) 10-31-99
to: Bronica List
After adapting a 180MM Zeiss Jena f2.8 Sonnar to my Bronica S2-A, I have
been diligent in aligning the focusing screen so that I can shoot sharp
portraits closeup at f2.8.
This led to a complete focus overhaul on the S2-A and other Bronica
cameras-
see these stories on Bob Monaghan's Bronica website:
http://www.smu.edu/~rmonagha/bronica.html
My study revealed that I am still battling film flatness problems common
to all 120 and 220 cameras.
Yesterday I attended the huge Photo Plus Expo at the Javits Center in New
York City, seeking to address this focus/film flatness problem will all
the new camera manufacturers.
In short, if my old Bronicas became unfixable what new cameras would I
buy?
I began with a chat at the Shutterbug exhibit with editor Bob Shell and
photographer/writer Jay Abend.
Both felt the newer cameras had better lenses and film flatness was not a
major problem. I stated unflatness still was in new equipment and that old
cameras could equal the new ones if they were properly aligned and the
inside surfaces of all lenses were cleaned of condensed oil from shutters
and focusing helixes. Jay Abend tended to agree but felt it would cost
$800 per camera. Too high I think, but much less than a new Hasselblad.
Hasselblad was my next stop and the saleman showed me the new focal plane
shutter 203-FE model with 100MM f2 Zeiss lens which he stated was sharp
wide open. It looked like an improved Bronica S2-A (current cost $500) and
cost of the Hassy outfit about $15,000. He opened the back and showed me
the new rollers and a spindle which puts drag on the feed spool to keep
the film flatter. A nice, expensive camera but still no new technology
for flatter film. Several other manufacturers have also now put a feed
spool spindle in their back inserts which puts drag on the film to combat
this problem. They are creating another problem as this puts stress on the
camera's wind gears and will strip or wear them out earlier, than if the
film traveled without drag on it. That is why old cameras did not have
this tension on the moving film.
Some of the other cameras I saw, include:
BRONICA SQ-AI - good design. lightweight, easy to focus on sharp viewing
screen
ROLLEI 6008- interesting design - film travels flat in back without bend,
may remain flat. But, release button on handle too small for adult fingers
and instant return mirror/motor advance blacks out too long
FUJI GX-680 III - Looked big, clunky and not well made - nothing new in
back to handle film flatness problems
FUJI GW 690 III - Leaf shutter noisy could not be used like an old
Rolleiflex for movie stills while shooting going on. Rangefinder poor,
small central patch, low contrast. Could be made into a good camera by
Fuji with improvements.
FUJI GA 645Zi- Autofocus 120 - difficult to tell where focus is set, not
solidly made.
MAMIYA 7II- Excellent Rangefinder 120 - Solidly made - easy to focus -
great to shoot weddings..
MAMIYA RZ 67PRO II - Big solid, easy to focus - good screen - great pro
camera recently seen on TV being used by Annie Liebovitz (spelling?) - no
special film flatness solutions.
PENTAX 67II _ revision of a classic - solid, well made, no special film
flatness provisions, but known for sharp pictures. Film travels flat
across aperture may contribute to sharpness.
The hit of the show for me turned out to be the CONTAX 645 AF.
Blake Ziegler of Kyocera/Contax told me that film flatness problems in
120/220 was the best kept major secret in the
camera business.
I then examined this camera which I feel is tops. He told me that with
their high quality Zeiss optics they had to seek a solution to film
unflatness. They had minor success with 120, which remains a problem. And,
why photographers like Jay Abend admit that they generally shoot at f11 to
have depth of field cover up film unflatness and other similar problems.
To this Bob Shell stated that focus shift in lenses presented a further
problem with stopping down. (ie. you focus wide open and stop down to f11
and the lens is no longer sharp at that setting). To which I replied that
one must always recheck the focus stopped down in critical photos being
taken.
Back to the Contax 645. With 220 film the camera has a small film back
insert that has a vacuum pressure late to hold the film flat during
exposure. This is the camera for sharp critical focus. 120 film still
remains a problem as the paper backing will not work with the vacuum back.
Bob Shell rarely uses 220 because not all emulsions are available in 220
and some labs that use dip and dunk processing, not machine processing,
must cut the 220 film in half to process, losing two potentially important
shots in the middle of the roll.
The Contax 645 autofocusing system works effortlessly from closeup to
distant shots. This is an easy camera to use.
I would buy this camera and their Zeiss lenses if my work depended on
crisp focus and fast results.
Going to Kodak, Fuji and Agfa the salesmen could not tell me which 120
Color negative film gave the sharpest images.
Minolta demonstrated their DIMAGE SCAN MULTI for me. This will scan
positive or negative film into computer (PC or MAC) from sizes from 16MM
to 6x9 cm. A $2000 unit, worth every penny. It can be sharp focused on
each piece of film and has software for many pre-scan adjustments.
I have tons of old 35MM and 2 1/4 negatives which I plan to scan into
computer and wish to print out on my printer. If I can make good sharp
8x10 prints this way, without the darkroom chemical smell or today's high
lab cost, I will be moving into this direction.
Capping this show off was visiting Saul Kaminsky at the KIEV USA booth.
There I purchased a superb Russian optical glass loupe (10X and focusing)
- a well made product for only $48 - far less than any comparable
products. I am using this to check my critical focus on 120 negatives and
slides and very pleased with this item.
All in all it was a good show and I am glad I attended it.
- Sam Sherman
From Rollei Mailing List: (y2k date?)
I have plunged headlong into Rollei TLRs, and find that a couple that I
have have backs with somewhat "flaccid" pressure plates. The plates have
behind them some tensioned strips that push the plate outwards, and the
whole works are fastened in place with two rivets. Now, it seems to me
that if one could push out the rivets, adjust the tension strips, and
rerivet the whole mess that would fix the problem. I am told by
independent Rollei repair people that the oversize rivets are no longer
available. I suppose I could take the thing to a machinist, but it seems
like such a simple fix if only one had the oversize rivets? Has anyone
else grappled with this issue, or is this really, really, arcane....?
Marflex said they sell the backs new...I didn't even ask what they cost,
as I am too young for a serious heart condition.
By the way, yes the pressure plates are indeed "flaccid". One can tell
simply by looking and touching them. Also, I interchanged with "good"
backs and the problem with lack of film flatness goes away. And, these
are the backs for the later 2,8 F's.
Cheers.
From Rollei Mailing List:
I recently aquired a Tele-Rollei. I ran test shots with and without the
glass plate. My observations of the results were:
-) The glass plate may improve the film flatness but I feel the benefit
is less than the focussing error. I could only detect a difference at
f/4.
-) The glass plate reduces contrast. Doing further tests showed that the
effect is a local one similar to "halation". This was confirmed by
placing a street light just inside the frame (night shot). The street
light showed classic "halation" effects with the effect extending beyond
the edge of the frame into the gap between frames. Repeating without glass
showed good control of flare and no noticable halation.
After doing the tests I will be using my camera without the glass. The
improved contrast results in what I regard as a better image. Normal
focussing accuracy accounts for more focus error than not having the
glass.
Richard.
--
From Leica Mailing List:
tedgrant@home.com writes:
When this kind of topic....."field curvature" comes up, may I ask
those
of you whom are knowlegeable and can readily identify what to look for
in a photograph and where this "lens character" can be seen. Please
post a description of what to look for and why it can be a bug-a-boo in
some pictures and mean nothing in others?
Field curvature is the lens' inability to focus all points of a plane
(such as a flat wall) on the film plane. This is usually manifested as
either the center or corners being in sharp focus, but not the two
together. This is not the same thing as a lens with decreasing resolution
away from the image center, where in that case no amount of focusing will
sharpen the corners. A lens with poor corner definition can have
substantial field curvature and it won't matter because the corners are
always soft, whereas a lens with superb overall resolving power but strong
field curvature will show the effects more obviously.
Why it means more in some pictures than others: 1. If you aren't focusing
a single, frame-filling flat-plane subject parallel on all axes to the
film plane, you won't see field curvature unless it is extraordinarily
severe (this is why so-called "flat-field" lenses are important mostly for
copy work and projection of glass-mounted slides). 2. Stopping down for
more DOF will reduce the effects of field curvature. Again, you can see
why a flat-field lens would be particularly useful in macro copy work,
such as photographing postage stamps (flat, full-frame subject, very
little DOF). Of all the "aberrations" a lens can have, field curvature
(unless it's quite severe) would be the one I'd worry least about. The
2-element 400 and 560mm Telyts (such as for the VISO and R-series), as
most achromats, exhibit quite high field curvature. But these lenses
aren't normally used for flat subjects. Wildlife or sports subjects
(central subject in focus, blurred background)would not be hampered by the
field curvature.
Hope this helps!
From Koni Omega Mailing List;
.....
Lyndon,
The 2x3 Crown Graphics are a great little camera - there are a couple in
the armoury here which get regular outings for architectural work.
You may find that the 90mm Hexanon is a bit heavy duty for the 2x3. The
101mm Kodak Ektar lens commonly found on these cameras would probably
rival the Hexanon if you could keep the film flat in the same way as a KO
back :-)
You may know this already, however the later lever-wind backs Graflex
backs are supposed to keep the film a bit flatter - there is probably not
a lot of difference between these and the earlier backs though......
Please keep us informed as to your progress in mounting the 90mm Hexanon
on a 2x3 lensboard.
All the best,
Clive http://www.cocam.co.uk
[Ed. note: why do we have such trouble believing brush-offs like
this? ;-)]
from: flexaret@sprynet.com (Sam Sherman) 9-23-99
to: Bob Monaghan
Bob,
Thought you would like to learn that while everybody who has ever made
120/220 cameras has generally had film flatness problems, Mamiya has magic
which protects them from that problem.
- Sam
----------
Dear Sam,
Thank you for your email inquiry.
We have not had a problem with 120 or 220 film sitting flat. The pressure
plate and the film tensioners of the film back holds the film flat against
the film plane.
Regards,
Chris Mynio
Date: Sat, 18 Sep 1999
All three major MF cameras have issues with their backs in regards to
frame spacing, frame touching, frame overlap or just running through a
whole roll no frames. Now if they could figure out how to produce one
continuous image on an entire roll end to end they wouldn't need frames.
Medium format APS, the ultimate panoramic camera. The proof sheet boxes
would be a little long though. They could also come up with an new paper
format for this one. Are you listening Mr. K. Take your best shot before
Mr. F gets a hold of this revolutionary idea. It could set the APS
mis-concept on the road to success.
Backs seem to be where they cut their costs. The counter and film
metering mechs are generally flimsy little devices. Mr. H's being the
best in terms of quality of material. But a brand new H back out of the
box often has erratic size spacing between frames. This is considered
normal.
A far bigger issue none of the big three MF makers address is film
flatness during exposure. This is an issue the consumer for the most part
is unaware of. The main intention of the consumer for going to medium
format is improved resolution and sharpness. If the film is not being
held perfectly flat during exposure the focus is not the same in the
center of the film as in the corners. Film flatness will also be affected
by temperature. None of the three offer vacuum backs.
A vacuum back will essentially compress the film perfectly flat across the
entire image area prior to and during exposure. This vacuum must then be
released to allow the film to move through the back for the next exposure
and the film must then be compressed for the next exposure. This would
require making the film back, body and lens completely air tight. A much
more expensive procedure that would most assuredly make everything more
expensive to produce, but decidedly much more precise.
This is only one of the many huge fudge factor issues regarding tolerance
issues in the manufacture of photo equipment. The makers of cameras get
away with it, mostly due to consumer ignorance of the issues. You are not
always getting everything you think you might be getting. Film flatness
with MF or larger is also a major issue when you take the film to the next
step, the enlarger. That is another story.
If you think cameras are overpriced for what you are getting, take a close
look at your enlarger with the light on the next time you are in the
darkroom. Extremely imprecise instruments to say the least, even the best
of them. This includes what they term the industrial ones, used by your
local lab. Some costing thousands of dollars. To say the least the photo
manufacturing industry is based on a system of smoke, mirrors and
illusion.
The perception of precision.
Best regards,
geoff/camera tech
From Rollei Mailing List:
Sean,
The flat glass feature was incorporated in 3.5 F at about serial number
2,230,000. From cameras that I have either seen or have, the flat glass
feature was dropped somewhere between 2,805,772 and your camera 2,823,951.
I have never seen any reference as to when this feature was deleted from
the 3.5 F but I am getting closer to narrowing it down.
As to why it was dropped - I am not exactly certain, but I think it proved
to be a reasonably useless feature in that it may have increased film
flatness, but at the expense of dust that would be caught between the film
and the glass and subsequently show up on nearly every frame. Since the
back was an option for these cameras, I would assume that Rollei could
tell the public wasn't buying into this option, and deleting the flat
glass mechanism from the camera would save them a wee bit on production
costs.
Todd
From Contax Mailing List;
Depth of field and depth of focus work differently. While stopping
down can increase depth of focus (at the film plane) this plane of
sharp focus is still very narrow. Vacuum backs have been standard
issue on aerial cameras for years since the film must be absolutely
flat if the images are to be sharp across the negative. I'd guess
that the vacuum back would make a difference on the 645 particularly
with the fast lenses when used wide open.
Bob
- ----------
From Contax Mailing List:
Since I need a 3rd back insert for weddings, I'm thinking about the 220
vacuum back. I see that KEH has 'em cheap, and two used ones.
http://www.keh.com/shop/product.cfm?bid=CM&cid=12&sid=newused&crid=527987
I'd like to compare results vs. the regular $150 120/220 insert, to see if
it increases sharpness in any way. Wait a minute, the 645 with 120Macro is
TOO sharp already. For tight head shots, I can see *every* tiny little
hair on the skin, and count pores. For less revealing photographs like
landscapes, etc a tad extra sharpness is always welcome, but certainly
already available in spades.
Has anyone tried this? Bob? John Coan? Chris?
Bradley Hanson
From Medium Format Digest (note date!):
Mamiya 645 is not the only one with this problem. It is actually more
common with the cameras in which the film path is straight (such as Pentax
6X7, Fuji rangefinders, etc.) I fought this with my Fuji for quite a
while until I figured out what the real problems are. There are two
causes. One is that vibration can cause film to come off of the supply
spool and when it does that it releases tension on the takeup spool and
the film can loosen on the takeup spool. The second is that there is a
very tiny difference in the width of the film backing paper and in the
distance between spool flanges between Kodak and Fuji 120 films. I don't
remember which is larger, now, but when I go from one brand to the other,
sometimes the takeup spool is just enough smaller so that it keeps the
film from laying perfectly flat on the spool. It is certainly very
important to keep your thumb on the supply spool when winding on the
first few inches of that new roll, but what do you do after you close
the door? Fortunately, the pressure plate usually puts enough tension
on the film to force it down between the spool flanges on the takeup
spool, but not always. (There is mfg deviation in every product.) I
had to bend a spring roller in my Fuji to put enough drag on the supply
spool to cure this problem completely. I would have thought that the
more tortuous film path in the Mamiya would prevent both problems, but
I would obviously have been wrong. Perhaps your 645 problem is something
else, but you might keep an eye out for signs of the problems I mentioned,
just in case they are happening to you.
--Brian M. Godfrey
From Medium Format Digest:
Hamish,
With regard to your complaint about your Calumet C2N producing curved
frame edges... here are two steps to locate the problem.
Get a straight edge and lay it along the four sides of the frame
cut-out and see if they are all straight. If they aren't, send it back
to Calumet. (They were straight on the C2N that I had.)
If the edges are pretty straight, find a dated roll of film to
sacrifice and load it in. Once properly loaded, remove the dark slide
and examine the flatness of the film. It should be flush against the
backside of the metal plate on all four sides. In the C2N that I had,
there was about 2-3mm gap at the take-up end of the frame that quickly
faded to no visible gap by mid-frame. This sort of exponential
approximation to a flat film plane causes the shadow of the frame
cut-out to describe a curved edge on the film.
Actually, the curve didn't bother me as much as the variation in
sharpness end-to-end... I sent my C2N back and got a Horseman roll
film holder, which is less convenient but works wonderfully well
(including even frame spacing).
Has anyone else tried checking their C2N this way. I wonder if I got a
dog or if this is standard issue....
[See also my response / summary below - HR]
Andy Cassino
From Medium Format Digest:
Fellow Medium Format shooters, I have a question to ask of
you.
DO you ever have focusing problems attributable to film flatness?
Reason. I bought two film backs for my 2x3 Speed Graphic, one
dating from 1955, the other from 1968. In use, I discovered a
large percentage of curiously out-of-focus pictures stemming
from the earlier film back. The difference between the two
was that the later back uses four rollers in the film path
where the earlier back uses only two.
The Graflex film backs are interchangable with those found
on the Mamiya RB67 (introduced 1970 - so much for Japanese
creativity). The film path is nearly identical to the
Hasselblad back.
tim
From Medium Format Digest:
I've been looking into this too lately. My older 6x9 back with no rollers
has an obvious problem with the film bowing out at the center, maybe 1mm
or so. The net result is that the center of the frame is focused too far
back, which unfortunately is compounded by two other factors - the
curvature of field of the lens and the tendency for the elements in the
corners of landscapes to be farther away than those in the center. I've
tried inserting music wire to simulate the roller - scratched film. Now
I've replaced the wire with a ridge built up from tape - about 3
1/8" strips of vinyl tape covered by a layer of the smooth brown plastic
package tape. No scratches so far, but still only slight improvement
in bowing.Fortunately I tend to use this back for horizon landscape stuff
mostly, so at f/16 or so I should end up with enough depth of field to
produce a reasonable negative. I've switched over to the newer backs
(actually cut down from 4x5 for my 3x4 Speed, since the newer style
was never made for that camera) for 6x7. I still see some variation in
focusing characteristics between the 2 backs I use, not entirely
predictable, which I'm still investigating. What the hell, there's nothing
else worth shooting this time of year besides test charts.
One technique I've been using with limited success is checking film plane
alignment and ground glass adjustment by setting the lens at infinity and
peering through the lens with a Nikkor 200 (on camera) focused at
infinity.
In theory the glass or film should appear in focus. You can put marks on
the film and stick a tiny flashlight inside the Speed to illuminate them.
I get some reassuring evidence using this approach, but on occasion it's
promptly contradicted by my next set of film tests.
--
Thorn Roby troby@carl.org
From Medium Format Digest:
.....
Tim, I have had this problem with the older Graphic backs expecially the
6x9 knob winds. Everyone told me that I was crazy and these backs have
given fine service for many decades. Never the less, inspection of the
film with the dark slide removed revealed a substantial bow in the center
of the film. This problem was solved by trading in the old back on a
newer (Singer) lever wind back. Incidentally, the opening on the newer
back was substantially smaller which probably enhanced flatness. I now
use Horseman backs which have a pressure plate. The Horseman backs are
much larger than the Graphic ones and some of the older Graphic Universal
backs have to be slightly modified to accept them.
Stephan Miller (smiller@world.std.com)
From Medium Format Digest:
I read in a German photo magazine that som pro's will put a film in a
camera not more than 20 minutes before the shooting because the film
flatness is low- ered, if it will stay in ther more than an hour or so. Is
that right ? And if I look on films in my Hassi magazines and observe the
reflections it seems to me that there is some waviness. Does this lower
the image sharpness ?
Peter Ochmann
From Pentax Mailing List:
Hey all,
I just read a VERY interesting article on film flatness at
http://www.smu.edu/~rmonagha/mf/flat.html
The article includes a test that you can do on your cameras. I
looked at all three cameras at my disposal (a Z1p, Z50p, and
MZ-10) and noticed that the film was indeed not sitting flat on
the pressure plate on any of the three cameras, but was slightly
warped (enough to be noticed).
Since I shoot at wide open quite a bit and notice that some of my
images appear to be in-focus in areas of the frame and out of focus
in other areas of the same frame, this would seem to be one cause
of the problem. With the lenses trying to focus an image onto a
theoretically flat plane, any deviation in that "flatness" would cause
the out-of-focus areas that I believe are appearing.
My question is this: Is there anything that can be done about this?
Send the cameras back to Pentax for a pressure plate adjustment?
The article mentioned pieces of glass in front of the film and vacuum
film holders (for MF) but I have never heard of anything like that for
35mm.
Any insight would be helpful.
Thanks,
From Pentax Mailing List:
Brian wrote:
If sharpness varies across the frame, you most likely are experiencing
film
flatness problems. I've never experienced it on my 35mm gear but my Pentax
645n needs care when loading Kodak film.
Or buy a new pressure plate. They are cheap I believe and also wear quite
a bit over time. I have three times replaced the pressure plate in my LX.
My Z-1p pressure needs replacement too since it is almost totally polished
now (so is the rest of the film chamber).
Contax RTSIII. A gizmo?
Pål
[ed note: some history of film flatness etc.]
From: Roger.G.Urban@ucm.com
I think I've told the story here before, so this time the abbreviated
version.
I got into photography because my father is an avid amateur
photographer and cinematographer. There were always cameras around
the house, mostly Exakta and Leica when I was growing up, but my
dad could never refuse a deal so he was always coming home with
something he had picked up in a swap or bought from a friend. The
first camera he let me play with was an old Aires rangefinder with a
fixed 50mm lens. What got me hooked was developing my own negatives
(black and white, of course) and making my own prints with his old
Federal enlarger.
My dad had a "thing" for German stuff. In those days most people
still looked down their noses and sneered at most Japanese cameras and
lenses. For his Exaktas he had CZJ and Steinheil lenses, considered
the best at the time. For the Leicas, Leica lenses of course.
Later when I "shifted gears" and decided to go into photography rather
than stick with science I still had that pro-German prejudice, but
could not afford really good cameras. My very first serious camera
was a Russian-made Zenit B SLR bought from Cambridge Camera for $
49.95 complete with case. That was a lot of money for someone earning
$ 60 a week! Later, after I proved to myself that I wanted to be
serious about photography, I saved up enough to buy a Mamiya 1000DTL
from J.C. Penney, which had a camera department in those days. The
Mamiya was the first camera on the market with both full average and
separate spot metering, and was state-of-the-art at the time. But
I still wanted German. (As an aside, the fellow who sold me the
Mamiya was Bryant Kling who went on to become a senior tech rep for
Olympus!)
After a succession of Japanese cameras I sold off everything and
saved up and bought my first Contarex, a "bullseye" or "cyclops"
model, already long in the tooth at the time, but with that amazing
thing hung on the front, a 50mm f/2 Zeiss Planar. A few years
more and I added some other lenses and my first Contarex Super
Electronic, the most advanced camera of its day built by Zeiss/Ikon
in Stuttgart. It had electronic shutter timing, add on motor drive,
auto-exposure (with an accessory), remote control, etc. With it
I got the 50mm Blitz-Planar, a lens which could be set with the
Guide Number of a flash unit and would automatically set the
correct diaphragm opening for correct flash exposure!
I used the Contarex system, added some Canon and a few other Japanese
cameras to my collection, and did a lot of commercial shooting until
the horrors of 1973 when Zeiss announced that it was shutting down
the whole Zeiss/Ikon works and would no longer make cameras. My face
was very long when I learned of that sad decision. When Zeiss did
not keep their promise to introduce new lenses in Contarex mount I
saw the writing on the wall and sold my Contarex system. To keep
using some Zeiss glass I bought into the Rollei system (I was already
using Rollei in medium format, the SL66) , but since
their system was somewhat limited I also expanded my Canon system.
In 1975 the first Contax RTS was introduced. Most did not take it
seriously because it was built by Yashica, and Yashica was known at
the time for a series of uninspired and not very reliable screw
mount SLRs. I saw my first one in late 75 or early 76, and after
handling it a bit I bought one. The camera was an "almost". The
shutter was a ground-breaking design by Dr. Sugaya who would later
invent the vacuum pressure plate system to improve film flatness.
But this first Sugaya shutter suffered reliability problems and
the camera's viewfinder was too small, showing only 80-some percent
of the image. Reluctantly, I abandoned the system and went instead
with the Rollei 2000 and 3000 series. I never owned the RTS II.
My return to the fold was ten years ago. I was invited to come to
NYC by Yashica to attend the introduction of a new camera. There,
after dinner in a nice restaurant, Bill Heuer unwrapped from its
purple velvet bag a preproduction RTS III. It was love at first
sight for me!!! I could not wait until they sent me a loaner from
the early production, and not long after, when they said they had
to have the loaner back (I kept it far too long!), I bought my
first one (well, "bought" by exchange, anyway). I still have it,
and my love has not diminished in ten years of use.
So that's my saga of knowing that Zeiss lenses were what I wanted
to use and spending a lot of years looking for the right camera
to put them on.
Bob
From Pentax Mailing List:
Hi All,
I mentioned this before:
Thomas Weber of Capaul and Weber told me that when his design team was
searching for suitable 120 and 220 roll film backs for the new Alpa 12WA
and 12 s/WA models, that some well known roll film backs have film
flatness errors of millimetres. The holders they ended up using for their
new cameras were:
Horseman and ArcaSwiss 6x7 and 6x9 - 120 and 220,
By the way the model 12 and 12s are completely manual in every respect and
are selling well worldwide. The price is astronomical.
D
From Rollei Mailing List:
As an SL66 user, I have never had any problem what-so-ever with sharpness
loss due to film flatness. I realize that this is an acknowledged issue,
but the depth-of-focus of a medium format circle of confusion, even the
stringent one used by Rollei (.0022"), provides more than ample
accommodation for film flatness errors.
Still, Rollei addressed this issue and Mannheim described a demonstration
that you could do to observe the flatness loss. With the SL66 he
suggested advancing a frame (using a waste roll of film) and quickly
removing the magazine from the camera. Immediately pull the darkslide and
set down the magazine with the film aperture face up. Position the
magazine so you can observe the reflected, mirror image of some contrasty
pattern, such as venetian blinds, on the film surface. About 30 seconds
after advancing the film you should be able to see the taut film relax
slightly and lift. Mannheim suggested that if you were concerned about
this that you might get focussed and framed and ready to go, and then
advance the film just before you shoot - exposing before the film relaxes.
I have two friends who use and like Hasselblads and they feel that this
happens with their magazines, too. We feel that the real issue, here,
isn't sharpness, but geometry. Architects and contractors don't want
their spec'd and delivered nice plumb and straight lines to be faintly
bowed. One of these guys showed me a couple of transparencies where a
doorframe located to one side of the frame was ever-so-slightly curved
(believe me, architects see this). The curve couldn't be seen on the
grid-lined groundglass.
Some high-end architectural photographers feel that roll film (120
typically) isn't flat enough for architecturals - that sheet film is
essential. Of course, they are probably as-of-yet unaware of the Contax
220 vacuum back. Isn't there a 220 vacuum back for the 6000 series
Rolleis?
Tim Ellestad
-----Original Message-----
From Rollei Mailing List;
Nope. The bending around actuall causes film to buckle, and not just
between the spools, but also within the confines of the film gate. Very
basic physics laws at work here.
-_______________
From Rollei Mailing List:
I've spent time talking to film people from Kodak and Fuji, and they
generally agree that a film path like that in Rollei TLRs, Rollei 6000
series, Fuji rangefinder cameras, etc., provides the flattest film.
However, the Rollei SL66 and current Rollei 645 magazines, as well as
Mamiya, Bronica, etc., don't seem to have problems with doing it
Hasselblad's way. The thing you must not do with a Hasselblad or
similar type magazine is shoot part of a roll and then put the camera
aside for days or weeks before finishing the roll. When you do this
the film curled tightly backwards over the rollers takes on a "kink"
and the frame shot on it will generally have areas that are out of
focus as a result.
Bob
Disclaimer: This message is not a criticism of Hasselblad. Bob
REALLY loves Hasselblad cameras.
----------
From Rollei Mailing List:
I hope your joking. Any bend will reduce the flatness in film. Even
Rollei prototyped a TLR that had a slightly different transport to avoid a
bend in the film (I believe this was in Rollei 75 years book). It is the
most compact way to do it, but even I would rather have a slightly larger
6000 film backs with flat film.
Peter K
-----Original Message-----
I think that "bending the film around," like with Hasselblads, is exactly
what makes the film lie flat.
From Rollei Mailing List:
Actually the way that film is set into the film chamber on a Rollei back
is every bit as effective in keeping the flim flat as it is in the
Hasselblad.
After being accustomed to loading Hasselblad backs for many years loading
the Rollei back did not come easy for me. Still, after shooting around 50
rolls through it since January it is somewhat easier. However, it is
still awkward! The built-in darkslide is a definite Rollei feature
benefit. Ease of loading the film is still to the favor of Hasselblad, in
my opinion. Hopefully it will become easier as I use the camera more.
Bob B.
....
From Rollei Mailing List:
No, it does not become flat. Cameras using this reverse curl film
path need all sorts of additional rollers and gimmicks to try to get
the film to stay flat. Try this with a junk roll: Load film into
magazine and advance to first frame. Take magazine off camera and
remove darkslide (you have to defeat interlock on some brands to do
this). Look at film surface and take a pencil point and press down
on film at different places on surface. If film is flat against
pressure plate it will not move anywhere you press pencil point
against it. If it gives, and gives more in some places than in
others, just remember not to use your lenses wide open on that
camera!!!!!!!!
Film flatness is a major problem with rollfilm cameras. That's why
cameras made for mapping and photometric purposes have vacuum backs
reseau plates, etc., to force the film to lie flat.
Bob
----------
From Rollei Mailing List:
No there isn't. I don't know if it is still available, but for a
while Rollei was offering a modified Mamiya 70mm back with vacuum
pressure plate.
Bob
....
From Rollei Mailing List:
----------
Some of the designers I talk to refer to things like this as gimmicks.
Non condescension intended.
Yes, a major problem, FOR THE DESIGNERS. And one of their major
concerns when designing and prototyping new film backs. This is one
reason so many different designs have been tried over the years.
Now with faster lenses being demanded by medium format photographers
it is becoming more of an issue.
Unfortunately, 120 film is much more difficult to hold flat because of
the backing paper, so a vacuum back (the simplest solution) will
not work. Since 220 has paper only at the ends, it succombs to
the vacuum and allows itself to be held flat.
Bob
From Rollei Mailing List:
The pictures look good because most of the lenses are only moderate
speed and rarely used wide open. Same is true for most medium format
systems. However, Zeiss has said that their lenses for 35mm give best
performance, particularly the very fast ones, when used with the RTS
III which uses a Sugaya-designed vacuum pressure plate. I expect that
the lenses for the Contax 645 system, which are absolutely state of
the art optical designs, will produce their best images with the
vacuum insert and 220 film, particularly when used wide open.
Hasselblad's solution to the flatness problem for photogrammetric use
is to install a glass reseau plate which holds the film against
the pressure plate, a design pioneered by Rollei years before in
some of the TLR cameras. All of the Hasselblad space cameras built
for NASA were so equipped.
Bob
----------
From Rollei Mailing List:
Totally different situation, Austin. Walter Zapp designed the Minox
with a curved film plane because that made the lens easier to design.
If you look at some of the cheap plastic point and shoot cameras,
typically the "focus free" ones you will find a curved film plane
in them as well.
But even though the film is curved in horizontal axis, it needs to
be flat in vertical axis.
In a standard high end 35mm camera the film is pressed against guide
rails by a pressure plate. It tends to bow out toward the lens, but
the amount of bowing and its location varies. Also, it may be flat
when first advanced (or relatively so) and bow out after a few seconds
when air has time to get between it and the pressure plate. When
shooting fast with a motorized camera film flatness is less of an
issue, as Dr. Sugaya discovered in his tests.
To design the lens to compensate for all of this is a ridiculous idea.
Believe me, if it could be done Zeiss would have done it.
Bob
----------
From Rollei Mailing List:
There is an informative discussion of film flatness issues in the Medium
Format pages (of particular interest to the 'Blad crowd.)
http://www.smu.edu/~rmonagha/mf/flat.html
I also had a long chat with Bill Maxwell about focus adjustment
between the taking and viewing lenses on TLRs. Choosing the actual point
of focus for the taking lens isn't as easy as you might think. Bill has
spent a lot of time peering through an auto collimator, and the focus
point should not be at the film plane, so the average repair guy with a
flat piece of ground glass at the film plane won't get it right. The
factory supplied a ground glass with a slight inset, to compensate for
film "bulge." My memory of Bill's method is that he uses film in the
camera, and takes a spot about a third out from center, as a good average
point.
Regards, Phil Stiles, NH USA
From Rollei Mailing List:
There are different schools of thought on this. Bill's method is one
but many repairmen use a flat ground glass and also get good results.
Another problem is focus shift, the fact that the focus plane of a
lens is different at different lens apertures. This is why you should
always focus an enlarger at the aperture you plan to print at, and
why experienced view camera shooters recheck focus after closing the
lens to the taking aperture.
Norm Goldberg patented an idea years ago which would have had a
linkage between the lens diaphragm and the support frame of the
focusing screen (he was thinking mostly of 35mm SLR). This would
move the screen the appropriate amount to compensate for the different
focus of the lens at viewing and taking aperture. The arrival of
autofocus made this a historical footnote since the AF algorithms
have a compensation built into them for each diaphragm setting.
Bob
----------
From Rollei Mailing List:
In all cameras used for photogrammetry film flatness is THE mayor issue.
In fact, while you can compensate for other defects (radial distortion,
uncertain focal length), no compensation is possible for the lack of
flatness of the film. The best overall solution is the use of a vacuum
pressure plate, but this is limited to cameras using a "naked" film, i.e.
a film without paper support; nowadays, only Contax RTS IV for 35 mm and
Contax 645 for rollfilm (but for 220 film only!) have such device
available.
The next best solution is a reseau plate between lens and film.
Ciao
[Ed. note: see Koni Omega Pages for more info
on KO/RO...]
Yes, they did, and an excellent design it was and is. They held the
film very flat by pulling it forward, letting it "relax" and then
pressing it firmly against the film aperture.
Bob
----------
From Rollei Mailing List:
Totally different situation, Austin. Walter Zapp designed the Minox
with a curved film plane because that made the lens easier to design.
If you look at some of the cheap plastic point and shoot cameras,
typically the "focus free" ones you will find a curved film plane
in them as well.
But even though the film is curved in horizontal axis, it needs to
be flat in vertical axis.
In a standard high end 35mm camera the film is pressed against guide
rails by a pressure plate. It tends to bow out toward the lens, but
the amount of bowing and its location varies. Also, it may be flat
when first advanced (or relatively so) and bow out after a few seconds
when air has time to get between it and the pressure plate. When
shooting fast with a motorized camera film flatness is less of an
issue, as Dr. Sugaya discovered in his tests.
To design the lens to compensate for all of this is a ridiculous idea.
Believe me, if it could be done Zeiss would have done it.
Bob
- ----------
From: Colin Monteith monteith1@sympatico.ca
Some brands like Contax offer vacuum 220 backs to keep the film flat. I
have never had a problem though with non vacuum backs for various MF
cameras and I suspect its more a case of people trying to get around bad
design. Hassy for one does not have any problems that I or anyone I know
has encountered with their backs.
Doug Spencer wrote:
From: w.j.markerink@a1.nl (Willem-Jan Markerink)
Bob Wibulseth bobbagum@bigpond.com wrote:
The 70mm back for Mamiya RB (and possibly Hassy, if only the rare
long-roll back) also have a vacuum pressure plate. With the RB, you need a
manual bellows (bulb?) to suck it vacuum, for each shot (and particulary
recommended after the film has sat for a while, halfway down the roll,
when the curling or bending is most pronounced).
--
Willem-Jan Markerink
w.j.markerink@a1.nl [note: 'a-one' & 'en-el'!]
From: "Q.G. de Bakker" qnu@worldonline.nl
"Willem-Jan Markerink" wrote:
The regular Hasselblad 70 mm backs don't. However, i have found two
Hasselblad 70 mm backs some years ago that had been modified to include a
vacuum pressure plate. Apparently done so by the Dutch "Meetkundige
Dienst, Rijkswaterstaat, Delft" (the survey department of the
traffic-ministry). Most likely used for airborne photogrammetry
applications, where absolute film-flatness is crucial.
Misschien bekend, Willem-Jan?
[Ed. note: the points about focusing accuracy on SLRs vs RF may be
interesting and useful...]
Takeshi Hashimoto wrote:
A while ago Erwin Puts posted the following on the maximum aperture that
can be focussed accurately at any given focal length with the various
Leica cameras:
Computations based upon physical baselength = 69,25 effective baselength:
M3=0,9 M2 etc = 0,72 M6J and M6HM = 0,85 (0,86 is also mentioned) I noted
in an earlier post that ALL M types share the same physical length of
69,25. Many persons give different figures for the physical baselength of
several M models (68,5 etc). These figures are not correct. Erwin -
-------------------------------------------
While the calculations are no doubt correct (Erwin wouldn't stand for
anything less;-)), there are a number of assumptions made in arriving at
these numbers. Whatever they are, if you apply the same assumptions to an
SLR with a good ground glass (split image and microprisms actually are
worse for accuracy) you come to the conclusion that you can usually focus
an SLR lens at its maximum aperture, just barely. If conditions are not
that good, maybe you should stop down. Focussing accuracy can be
increased, of course, by putting a magnifier behind the eyepiece.
To get to the point, with the poorest of the M's re focussing accuracy,
the Noctilux is well within the capability of the camera, and the .85 and
M3 have a stop or more to spare. An SLR does not do as well.
Also, autofocus systems do not do quite as well (yet) as manual focus on
SLR's, so you're gambling if you use your lens at maximum aperture with AF
on your AF camera.
From Contax Mailing List:
There is something about this in the latest Zeiss newsletter.
Basically it says that lenses have not been as good as they could
be due to the fact that film simply did not lie flat enough to
make it worth the lens designer's while to spend the time correcting
for flatness. Since digital sensor chips are VERY flat, this offers
the lens designers an opportunity to really show off what they can
do.
Here are the exact words:
" Due to the three-dimensionality of the image receiving film surface
it is rather questionable to put special effort and cost into
redesigning lenses to achieve even higher flatness of field or
reduced secondary spectrum. Digital image receivers, on the other
hand, can be made to achieve and maintain a higher degrees of
flatness. "
They say the flattest fields are in the Planar, Biogon, Sonnar, and
newest Distagon designs, making them ideal for digital photography.
Bob
From Contax Mailing LIst:
Bob Shell wrote:
I'm so glad Zeiss is tracking the cutting edges of
digital/photography here. It has been so frustrating for me as an engineer
to know the infinite potential of theoretical design possibilities and be
forced to stare in the face the limitations of present optics and digital
media which is largely due to prior manufacturer marketing, inventory and
largest consumer niche/gross sales considerations. Engineering wise, I
went with the Zeiss/RTS III for its vacuum back which in keeping the
film's plane as flat as currently possible, at least theoretically, gives
me the very best that traditional and present film and optics technology
has to offer in 35mm in terms of accuracy and amount of information
captured. But, requiring a flat plane would seem, in part, due to present
lens designs directing light to a single place of focus in the center to
be received by the film.
However, theoretically, digital sensors themselves do not
necessarily have to be flat or lie in a perpendicular plane in order to
capture all light information presented. Ironically, light photons can
simultaneously be observed to travel in waves (analog) as well as packets
(digital)!!! And, their can and are multiple or infinite places of focus.
Others have mentioned the fly's eyes or compound planes and points of
focus. For example, the new Fuji sensors do not lie in a flat plane.
Thanks for providing this profound insight into current Zeiss
thinking Bob. It definitely gives us tangible hope that CZ may well be on
their way to developing what would have to be considered as . . . the
ultimate digital tour de force! Can we wait that long? I'll be checking
out the Sony 3.3 when it hits the distributors to see if CZ's consumer
lens is any good.
Best Regards,
Ben
From Contax Mailing List:
Maybe. But in photo equipment tolerance terms, a deviation
of 0.1 millimeter would be like buying a car and finding
that one of the wheels did not touch the ground!! This is
a really BIG measurement in the critical lens to film distance.
I don't know the official factory tolerance on this measurment
from Leica, but I just pulled out the shop manual for the
Rollei SL35E as an example, and the flange to film plane
distance is 44.67 (longer than Leica M because this is an
SLR) and the tolerances are from +0.02 to -0.01.
Muchan, you may want to look in the Contax repair manual you
bought and see what sort of tolerances they allow in this
measurement. My guess would be that Leica M tolerances are
tighter than those for SLRs where focus is confirmed directly.
Bob
...
From Koni Omega Mailing List:
Martin F. Melhus wrote:
You can find a good selection of 6x9 folders this way, 6x12 is also a
possibility. I was looking at an old folder with this in mind about 6
months ago, however the shutter was a little sick and the lens didn't
appear to be worth the time and effort.
The KO film holder is probably one of the best designed/engineered ways of
holding film flat - this more than likely accounts for some of the high
resolution corner results from lens tests. The ultimate pano camera would
be a 6x7, 6x12 or 6x17 KO wideangle with a switching mask for the various
formats and a redesigned set of 58/60 rear elements to remove the
mechanical vignetting. The larger lens throat required for the wide
formats
would allow full sized rear elements.
Guess it ain't going to happen..... now where did I put that hacksaw ;-)
All the best,
Clive http://www.cocam.co.uk
From: Harald Finster finster@ave.ac.agit.de
OorQue wrote:
[lens performance LF vs MF]
Probably you can't generalize here.
In theory MF lenses should be better than LF lenses due to
the larger image circle.
I have personal experience with a Zeiss 110 2.0 compared to
the 110 5.6 Super Symmar with landscape images.
I did not carry out any 'formal' comparisons but the 'subjective'
result is, that I prefer the Symmar.
Probably landscape photography requires more than pure
resolution and contrast - just speculating.
Film flatness seems to be a very important issue when comparing
LF to MF: I compared the Super Anguklon 47 XL with a Linhof Back
to the Zeiss 50 and the 50 seemed to be much much sharper until I
noticed, that the film flatness of the Hassi back is far better
than that of the Linhof (6x9) back.
This seems to be the limiting factor especially with very
short focal lengths.
Greetings
Harald
From: dickburk@ix.netcom.com (Richard Knoppow)
"John Stafford" John@Stafford.net wrote:
The aberrations generally scale with focal length. So, if one
measures the aberrations in terms of _percentage of FL_ they will be
the same regardless of FL. However, in terms of absolute resolution or
MTF the shorter FL lens will be better by the scaling factor.
Since the image magnification is also a function of FL the
difference in resolution may make little or no difference in the final
image since- presumably- we are talking about final images (prints) of
the same size, so the large format image needs less magnification.
To get the same resolution in a 300mm lens as in a 50mm lens, which
are otherwise similar in coverage angle and speed, would certainly
require a complete re-design and likely a more complex lens.
I am not really sure what medium format means anymore. When I
started in photography, back when you had to dodge dinosaures to get
to the street car, 4x5 was "medium" format, and maybe even 5x7.
Certainly there is much less difference in going from, say, 6x7cm to
4x5 inches than in going from 35mm to _anything_ larger.
I think in general 4x5 is about the point of diminishing returns, at
least for ordinary size prints.
---
From Rollei Mailing List:
you wrote:
Most lenses are designed to have as flat a field as possible. For
pictorial lenses sometimes a comporomise is made between field flatness
and astigmatism. Its possible to minimise astigmatism by allowing a little
field curvature. Lenses for copying or enlarging must have an absolutely
flat field but pictorial lenses are a little more tollerant.
Some caution is needed in measuring field flatness in a camera,
especially a roll film camera, where the film flatness may not be perfect.
Two cameras and two different rolls of film are involved with this
comparison so there are some other uncontrolled variables here.
It would be interesting to see what samples of the two lenses did on
bench tests with proper targets which could emulate infinity.
There are a large number of lenses analysed in _Modern Lens Design_
Warren J. Smith, McGraw-Hill Book co. Among them are a large sample of
Planar-Biotar types. The perfomance varies among rather similar looking
lenses so it is not surprizing that differences can be observed in very
similar actual lenses.
Field flatness does not vary with the stop. However, it its effects are
minimised by depth of focus as the lens is stopped down.
There are other effects which may be confused with field curvature. The
primary one is astigmatism. Probably coma is also a factor. Astigmatism
results in two points of focus. At one, a point object is reproduced as a
section of a radial line, at the other as a segment of an axial line. The
point is reproduced as a round blur spot at a point between these two.
Astigmatism in a modern high quality lens should be vanishingly small.
Coma is the reproduction of an off-axis point as a tear-drop shaped
blur spot. The narrow end of the spot can point either way along a radius
toward the center. Coma is eliminated by stopping down, and is cancelled
in exactly symmetrical systems. Lenses of the Biotar type have very little
coma.
----
I just got the latest issue of Zeiss Camera Lens News.
There is a very interesting but brief article about
Zeiss developing a special computerized microscope to
measure film flatness to an accuracy of 1 micron in
medium format cameras.
They say their testing of all cameras is not completed
yet, but they can make two statements at this point
in their research. First, 220 film usually offers better
flatness than 120 "by a factor of almost 2", and second
that running the film through the camera quickly is
imperative in maintaining flatness. "Five minutes between
exposures may be some sort of limit, depending on brand
and type of film. 15 minutes are likely to show an
influence of bending around rollers. Two hours definitely
will."
So, for maximum sharpness in medium format, always use
220 film and run the entire roll through the camera
relatively promptly. Many of us already knew that, but
it is nice to know that objective testing by Zeiss has
verified it.
Bob
From Rollei Mailing List:
....
This is interesting. I was taught very long ago to wind the film as
shortly before making an exposure as possible. Evidently a good rule.
----
From Rollei Mailing List:
Richard,
I adopted the same rule while using cameras with no double exposure
prevention. I could never remember wether I had really wound the film
or not. So I started advancing the film just before shooting. Now I
know I wasn't just working around my early senility, I was making
sharper pictures.
Gene Johnson
From Rollei Mailing List:
Interesting thread. This is the opposite of 35mm film, where the
cartridge lip causes a bulge in the film which relaxes between shots
see Norman Goldberg, Shoptalk, Pop. Photogr. May 1986, p.82; wherein the
0.08mm film bulge in 35m drops to 0.04mm after waiting 30 minutes for
film to relax, a result reported to Mr. Goldberg by some Zeiss scientists
regarding 220, I recall a similar recommendation in the August 1999
British Journal of Photography series on film flatness; they also
recommended 220 over 120 as it improved performance in their tests...
Date: Thu, 10 Aug 2000
....
It has always been my understanding that since some of the rollers are on
the body of the magazine which contact one side of the film and another
set of rollers are on the insert which contact the other side of the film,
the spacing between the rollers in the magazine body and on the shell
insert are very critical for best film flatness. How much of a difference
this will make in practice I don't know but apparently that is the reason
why each magazine body is carefully matched to a corresponding insert
shell. With the amount of money invested in a Zeiss lens and Hasselblad
body, I would guess it is a good idea to make sure the serial numbers
match.
from: flexaret@sprynet.com (Sam Sherman) 8-5-2000
Bob,
Anyone who has a history of use of 4x5 equipment knows
the problem with film-UNflatness is in the film, not the cameras or
the backs.
In shooting 4x5 film in film holders, many types
of sheet film were on a stiff film base support. The processed
negatives would lie flat. The old film packs which used thinner films
attached to paper leaders which moved around in the film pack adapter,
had to by nature, be thinner to curve around. These processed negatives
rarely lie flat.
120 and 220 roll film, to fit on the small 120 film spools, must have
film that is thin enough to roll up on these spools and be able to
curve through the film path with rollers in various 120/220 cameras.
If the film were thicker and stiffer it might be flatter at the film
plane, but it might be too thick to roll up on a 120 spool.
This unflatness problem would explain why
Pentacon made special backs for Pentacon 6 cameras which would take
glass plates (probably 2 1/4" x 3 1/4" or 6x9 cm - taking a
photo only in the the center of that plate). This for critically sharp
scientific work, which rollfilm would not be good enough for.
So.....
this problem should be thrown back to Kodak and the other film companies.
To make a better 120/220 film support, which while thin enough to roll
up on a 120 spool, would also magically lie flat in the film gate.
- Sam Sherman
From Contax Mailing List:
I just got the latest issue of Zeiss Camera Lens News.
There is a very interesting but brief article about
Zeiss developing a special computerized microscope to
measure film flatness to an accuracy of 1 micron in
medium format cameras.
They say their testing of all cameras is not completed
yet, but they can make two statements at this point
in their research. First, 220 film usually offers better
flatness than 120 "by a factor of almost 2", and second
that running the film through the camera quickly is
imperative in maintaining flatness. "Five minutes between
exposures may be some sort of limit, depending on brand
and type of film. 15 minutes are likely to show an
influence of bending around rollers. Two hours definitely
will."
So, for maximum sharpness in medium format, always use
220 film and run the entire roll through the camera
relatively promptly. Many of us already knew that, but
it is nice to know that objective testing by Zeiss has
verified it.
Bob
From Contax Mailing List:
Blake did not know, but said there MAY be a vacuum back for the N1 as an
option. He thought they left it off to control cost on an already
expensive camera. Hopefully they will offer it later for those who would
like it.
Yes, I suppose the subtext of their article about film flatness was "use
the Contax 645 with 220 and vacuum back and don't worry about it."
Bob
...
From Rollei Mailing List:
you wrote:
Bob, they mention going around the rollers. Does this mean
Zeiss is testing with magazines like the hasselblad one?
Some cameras which don't use Zeiss lenses don't bend the
film before exposure, if my memory is good. Ed
Years ago I had a brief infatuation with a Minolta Autocord, in which film
ran from top to bottom. This meant that it came off the roll into the
focal plane before rounding the bend on the bottom after the exposure.
There was some speculation this would improve film flatness. In practice,
I never tested the proposition or was aware of any sharpness variations.
Almost everything came out very sharp with both Rollei TLR and the
Minolta. It could have been accounted for by my usage, mostly
photojournalism (this was in the 60s), which meant a lot of pictures taken
rapidly, for the most part.
These days I use Hasselblad , Rollei TLR and Mamiya 6. Film goes through
all of them pretty fast, so I guess I have been riding the high side of
this thing pretty much by chance. But the Zeiss film flatness research
might explain a phenomenon the has until now completely mystified me.
I was shooting several very large groups with Rollei 3.F and Hasselblad.
It was one of those once a year events that absolutely, positively had to
come out, no excuses accepted. So I alternated cameras, 2 exposures each,
had films developed in 2 batches (and well I did, one roll was ruined by
my photofinisher, first time in 20 years!) All the 'blad film came out
satisfactorily sharp. Most of the Rollei was about equal to the 'blad,
except that almost every other pic on each roll came out SENSATIONALLY
sharp!
The enlargements looked like from 4X5. Better!
The way the day went was I would wait for a group to set up, make 2
exposures each camera, and then wait an hour or so for the next group to
assemble. Due to my customary PJ practice, I always wind on after each
exposure ( in fact, I can't seem to stop myself from doing so after 46
years of working that way).
So the first exposure each set was on film that had settled in place a
relatively long time while the next took place seconds later. It didn't
seem to make much difference on the blad, but with the Rollei, Wow!
Can it be that this mystery is now solved?
From contax mailing list:
Well, if you ask the Hasselblad list the same questions I'm sure you'll
get a lot of replies. Ditto for the Rollei group. Some of us here own
Rollei and/or 'Blad as well. I have the Rollei 6006 and lust after the
6008i. I use the 80 and 150 CZ lenses on it. The meter on the camera is
very good, but they really improved it on the 6008. Film flatness on the
6008 is supposed to be better than on Hasselblad, especially near the
edges as Rollei holds the film better/flatter. As to which format is
better, it's a toss up. 645 gives you more pictures per roll, which is
attractive to me. Gepe glass slides for 645 and 66 are not too much
different in price. Much cheaper than the 67 glass slides. 'Blad has an
older design, but allows you to buy from the used equipment market and
rental is much more available. Rollei has not the same market
distribution, by which I mean not too many places rent it, and less used
equipment for sale. Both are pretty expensive. Rollei has a battery that I
a! bsolutely hate. Costs me about $175 to replace. The Blad 503CW uses
commonly available batteries. The Blad viewfinder looks brighter to me and
easier to focus. Rollei has sexy red LEDs that show you f/stop and shutter
speed, and many more modern and useful options on the camera body.
Then, there is Contax 645, the new kid on the block. It appears lighter,
handles quicker and eats batteries for breakfast. Slap a 35mm lens on the
645 and look at the landscape. You'll swear there is a polarizer on it -
there isn't - because the multi-coating is so good.
Lenses for Contax 645 get very high marks, and you'd probably never be
able to tell whether or not the picture was taken with Hasselblad or not.
Good luck trying to figure this out. I think the only real solution is to
buy a 503CW, a 903SWC, a 203FE, a 6008i and a Contax 645. Deep pockets, my
man, deep pockets are needed! 8-) LOL!
From Contax Mailing List:
That's interesting. John Winchcomb, reporting other research in BJP (15
dec 99) came to exactly the same conclusions. FWIW he produced some plots
for the 6 x 4.5 format that showed 'typical' departures from the film
plane of some 125 microns, with peaks aproaching 500 microns for 120 film
(effects of lack of flatness plus poitioning error). B&W negative film
seemed to be less susceptible to the 'kinking' effect due to the rollers
than was transparency film. He claimed the results were representative of
current high quality cameras, but the vacuum back was not tested.
It is evident that film flatness is the one thing that limits the
resolution achievable in medium format (at least for large apertures) and
will need to be improved to realise the full potential of modern lenses
and film emulsions. It will be interesting to see the Zeiss results and
to see how far the vacuum back achieves this.
From Rollei Mailing List:
The problem with film taking on a "kink" when left
in the magazine too long before advancing is more of
an issue with "reverse curl" film paths like Hasselblad,
Bronica, Contax 645, Mamiya 645 & RB/RZ, Rollei SL55,
Rollei 6000 series new 645 back, etc.
Cameras like Rollei TLR, other TLR, Rollei 6000 series,
Kowa 66, etc, which use a straighter film path with
only a little curl probably hold film flatter.
Cameras like the Fuji rangefinder models probably hold
the film flattest, but are hardest to measure since the
lenses don't come off.
My informal tests involve simply pushing on the film
in different places with a pencil point and watching
whether there is any "give". Easy to do if you can
get the lens off.
Bob
From Rollei Mailing List:
Yes Ferdi, the roll is a problem. If you unroll a roll of 120
film and carefully examine the surface from front to back
you will find that...near the end of the roll the film has
wrinkles in it. This is the part that is closest to the core of the
reel. Tests made by Simon Nathan, some years back, revealed
that the frames in the beginning of the 120 roll could
be sharper overall than the frames in the end of the roll.
620 film has a much smaller core...much worse. Ed
From Contax Mailing List:
The Rollei 6000 series should be the best for this since
they have a straight spool to spool film path with no
kinks.
Bob
From Leica Mailing List:
The PlusX ended slightly behind the D100, grain was just visible, but
acutance was very high, giving the pictures a high level of impact, which
would be excellent at enlargements just till 10 times.
DD-X is a classical BW developer and has no relationship to C41.
Zeiss has just released data on film flatness with
120-film (their 65 system). Conclusion: 120 has serious flatness problems.
Best solution: use 220 and make sure the film is transported quickly. When
a film is left in the camera for more than 5 minutes without movement,
flatness is reduced and when the film is in the camera for more than an
hour without transport, serious trouble can be expected for that frame.
Minolta does not plan a revamped CL. Of course it is easy for Cosina to do
a Bessa-R with M-mount. Does it make sense? I doubt it.
Leica company report for fiscal year ending march 2000, shows a profit and
a strong base for further development.It is clear that Mr Cohn is on the
right track and that he knows where he is heading for. Mr Erfurths
negative comments, repeated ad nauseam, are unjustified and unfounded. And
his predictions for the new Leica products are probably as wrong as his
comments on Mr Cohn's abilities. In the imaging field, the company will
always be a small player, but so are Cannondale bikes in the bicycle
world. But you can survive and even prosper.
Erwin
From: bhilton665@aol.com (BHilton665)
I recall him saying he felt he got *better* results from 6x7 than he did
from his earlier 4x5's *in the field* because the film plane was flatter
and because he didn't have as many problems with wind (tank-like Pentax
6x7 vs the bellows of the 4x5). Of course he doesn't do the extreme
'near-far' landscape shots a la Muench, Dykinga, Clifton that require
movements either.
As Jack Dykinga recently remarked "The 'decisive moment' with 4x5 is when
the wind stops blowing!".
From Minolta Mailing List:
Very interesting article from the Anstendig Institute entitled,"WHY NO
CAMERA
CAN FOCUS or THE CRUCIAL MISSING LINK IN PHOTOGRAPHY AND OPTICS
copyright 1983 The Anstendig Institute.
If you're really interested on cameras actually focusing and the
technology
behind it then take a look at: WHY NO CAMERA CAN
FOCUS
I bid you all adieu
Bill B.
From Rollei Mailing List:
Is there a definitive guess as to which camera bodies had the flat glass
and which did not? I was talking to a friend about Tele Rolleis and I know
that my several Type 1 Tele have the option, while some of the Type 2
(none
at this time in my collection) do not have it. Same for the 2.8F cameras,
where after a certain point the option was no longer available.
Andrei D. Calciu (VA-4270)
From Rollei Mailing List:
John,
have you used the flat glass much? I was not very happy using it in one of
my 2.8Fs. The highlihgts, especially light sources on night shots looked
wierd. Clearly some unhappy influence from the glass, as without the glass
insert the lights looked just fine, displaying the usual start pattern.
Andrei D. Calciu (VA-4270)
From Rollei Mailing List:
In all fairness, I do not think the glass insert is a great invention. It
certainly does bring a benefit when doing macro work, keeping the film
from buckling, but for everyday shooting, it is a pain in the royal
behind. It needs constant cleaning, it may at times mar the film and it
does mess up highlights by creating a strange halo-like effect around
them.
Andrei D. Calciu
From Rollei Mailing List:
you wrote:
This is similar to the halation problems early glass plates had. It
probably could be cured by coating the glass with anti-reflection coating
like lenses or filters. It might even be economical to to coat existing
plates since the plates are simple planes and need no rebuilding,
recementing, etc., as a lens does for coating. It might be worth checking
with someone who offers a lens coating service. The only one I know of in
the US is John van Stelten, but there may be others. Multicoating would be
ideal, but is probably beyond doing aftermarket, but even simple single
coating would reduce the internal reflection and haloing substantially. I
wonder why Rollei didn't do this in the first place.
I'm sure most know that the glass will increase the effective focal
distance by an amount equal to about 1/3rd the thickness of the glass. For
really precision work this should be compensated for.
----
[Ed. note: Mr. Ralph Fuerbringer is the creator/craftsman behind the Vistashift 612 Panoramic Camera...]
Before you spend much on glass in front of film you might check out the
reports of image degradation from glass in the hasselbad polaroid holder.
As I recall the definition in the center was noticably degraded while the
extremes lost more than 60%.
I have a holder 6x17 with excellent film flattening. Remember the
pressure plate does not ride on the film itself or the paper backing. The
side rails are slightly higher in all cases. Rollers at both ends are
helpful as are snug winding spools at both ends.
ralph
Date: Fri, 15 Sep 2000
My Horseman 6 x 9 cassette for 220 roll film that I use on an
Arca Swiss 6 x 9 FC camera, exhibits a severe film flatness
problem. I loaded a roll of Velvia, removed the dark slide
and had a look. Upon loading or advancing, there is a pronounced
bulge in the film in the third of the frame closest to the
advance crank. After about twenty minutes, the bulge will
nearly disappear. With a digital caliper, I tried to
measure the height of the bulges and got as much as 0.45 mm.
I inspected the cassette and found nothing misaligned or bent.
Therefore I don't really think that my Horseman cassette is
particularly bad.
- have you had similar problems with 6 x 9 cassettes?
- based on 0.45 mm film bulging, do you feel that this cassette is bad?
- is 220 generally worse than 120 in such cassettes?
- are there 6 x 9 cassettes specifically good in terms of
film flatness? Linhof perhaps?
- are there even roll film cassettes with vacuum?
At this point I'm quite desperate for a solution as I
feel like I'm wasting my energy with this Horseman
cassette. Therefore thanks much in advance for all help.
Frank Loeffel
Date: Thu, 28 Sep 2000
There are some issues regarding film flatness and 120 film in film backs
for some cameras. Kornelius J. Fleischer or Zeiss posted this in another
forum on June 29, 2000:
"At Zeiss, we have dived into the mechanical tolerance systems of
cameras, film guides, roller arrangements, viewinders, focusing screens,
slr mirrors, the effects of temperature and humidity. They all
contribute. We found that film unflatness is one of the worst influence
factors of all. With newly developed equipment we recently confirmed
that 220 film offers better flatness in magazines for Alpa, Contax 645,
Hasselblad, Rolleiflex, Mamiya."
You may need to remove an underscore to reply directly.
From Rollei Mailing List:
Sorry but I cna't sit back and take this Leica bashing anymore, and I have
to say I take exception to your remarks of Leica that "they" ( I presume
you mean the people at Leica)"don't really care." If you had taken a
little more time to load your Leica you wouldn't have missed your nice
picture shooting day. I've load many rolls of film through my M6 and
haven't had any problems. In fact the system appears to provide for a more
positive and flatter film registration than any other camera can provide
except for perhaps a sheet film camera.
I'll will add that easier doesn't necessarily mean better.
"Kotsinadelis, Peter (Peter)" wrote:
From Rollei Mailing List:
Jay and all,
The one thing I may have not made clear in my focusing post was that Bill
Maxwell puts a roll of film in the camera and then uses his scientific
instrument to determine the focus by taking readings off the film's
surface.
That is why I mentioned that he has used many different films - they all
have different curling/buckling characteristics. The football shaped bulge
that I mentioned is what he determined by taking lots of readings off the
films.
HTH!-Fred
Jay Kumarasamy wrote:
...
From Rollei Mailing List;
From memory, the maximum plate thickness you can put in a R-TLR cut
film holder is about 2 mm. But 1mm was apparently a standard glass
plate thickness if I can judge by the size of old glass plates
(106x44x1mm) for a stereo camera I have seen recently. Actual plate
thickness is not an issue as long as you can clamp them in the R-TLR
back since you bring the plate in focus with a spring system. If you
are afraid by the potential lack of flatness of 120 rollfilm (see the
last issue #10 of Zeiss's "Camera Lens News" on www.zeiss.de) using
glass plates is *the* solution to get the maximum sharpness from your
beloved TLR taking lens. ;-);-)
I've never used regular 6.5x9cm glass photographic plates in my R-TLR;
however I've used as a student 6.5x9 AGFA holographic plates as well
as Kodak high resolution plates 3" (63.5mm) square about 1.5 to 2mm
thick. For high precision applications people in optical engineering
preferred very thick (~5mm) plates for maximum flatness and optical
quality. Unfortunately even if the abovementioned examples are still
on catalog this is not at all a cheap source of glass plates for
coating them at home.
--
From Rollei Mailing List:
Jay Kumarasamy wrote:
The Loooooong reply:
I spent a lengthy phone call discussing focusing with Bill Maxwell today.
Why? Because the simple focus test that I use on all my rangefinder & TLR
cameras, that had always worked well for me, had indicated the point of
focus on the E2 that I just got back with new screen was falling two or
three inches behind where I thought I was focusing on the viewing screen
from about 4.5 feet away. I use a wooden board about 12"x12"x2" thick with
grooves cut across the top every inch. I place a playing card in each slot
starting from the front right, with each card covering half of the card
behind it. All the cards are black with the ace of spades in the middle -
this is the card I focus on. I then expose a frame wide open. When the
Queen two cards behind the ace came out in sharper focus than the ace on
the negative I called Bill.
Here is what I learned today:
1. Check my own ability to focus on a matte screen (without a split screen
or microprism) by putting the camera on a tripod and focusing over and
over again on the same spot. See if the focus/distance scale winds up in
approximately the same place (closely clustered) each time. You can put a
piece of tape on the wheel and mark it with a dot each time if you need
to. Once you have verified your ability to focus (this is not a skill, it
depends on the condition of your eyesight) you can then proceed to the
next step. BTW-I always focus with built in magnifier and all focus tests
are done with camera tripod mounted and using shutter release cable.
2. Put film in the camera and focus on something like my little focus
testing setup very carefully, then shoot the entire roll. This was his
suggestion based on his opinion that each frame in a
roll buckles
differently and can therefore display different points of focus. I knew
about the buckling/warping phenomenon already, but thought that
technicians took this into account when calibrating. I even knew about not
winding the film until you were ready to take the shot for optimum
flatness, but I had never heard of different frames on the roll giving
better or worse focus.
Bill believes the first frame is the worst offender and the others can
vary all over.
Here's what I found from further experiments:
1. My ability to focus was acceptable, it does take more care in close up
low light situation. I also found I could focus the new bright screen to
the same position that I got when I replaced the original screen with
split screen.
2. The test with entire roll and careful focusing saw insignificant
differences in point of focus between the first frame and the eleventh.
And, my point of focus was much closer than my first test, with my Ace and
the card behind it both being in acceptable focus. I would judge that my
focus may have been off one half inch at most at 4.5 feet. That seems to
be within acceptable limits for me, as it would easily be within focus at
smaller f-stops.
Bill's explanation: that it may have been that I was focusing with the ace
dead center in the screen. He sets the focus based on a
point about 1/3 off center to take the buckled film into account and sort
of average it out. This makes sense to me. He suggested I shoot the same
test again but place the Ace (focus target) about 1/3 above or below
center. The film buckle seems to have a football (American football) shape
to it. Thats why the above or below, rather than side to side. Bill
Maxwell told me he would be happy to recalibrate the focus at know charge
if I still wanted it. I don't, I am satisfied.
HTH!-Fred
Date: 16 Sep 2000
I have been "maneuvering" to scale my LF system to a 6x9 (absolutely going
to keep the 8x10 though) primarily for the convenience of roll film. I am
pretty disappointed to read the "reviews" and comments of experts that
seems to clearly show this film flatness issue to be worse in 6x9 systems.
It appears that even 4x5 with RF backs are better (Oy). There goes my
Ebony SV23.
This problem with Horseman RF holders is disconcerting. Horseman stuff is
not inexpensive and my; understanding is that they OEM the Arca backs.
Linhof backs may be better but they onlyl fit Linhof cameras and $$$. The
Linhof TK23S is no great alternative to light 4x5 cameras (although it is
an engineering delight) Having cut film holders is counterintuitive in
6x9 but an obvious alternative. I found a coupleof Linhof holders which
use pressure plates and is fine. A grafmatic is known for film flatness
and they are available. Unfortunately, there is only BW film out there in
sheet form.
My suggestion is that you consider discussing this with the Horseman
distributor and see what their tolerances really are. Challenge them to
"spec up" your RF holder. I bet you could post some "nice" attention
getting messages on the appropriate message boards that could stimulate
their interest should they initially demur. We could make one hell of a
racket (God bless the internet). They or possibly you could publish or
post those tolerances on the boards and all of us could hold their feet to
the fire.
My guess is that 120 backs are not as bad, but this is just anecdotal.
You may just need to load your back and wait the 10 or 20minutes for the
film to "relax"( in the interim). Let me (us) know how you do and if I
(we) can help you by amassing the hundreds of millions of LF users to give
support.
Keith
Date: Sat, 23 Sep 2000
vilntfluid@aol.com (VILNTFLUID) wrote:
Arca backs are indeed Horseman, but they come in 120 only,
not in 220. I don't know whether this is due to film flatness
issues or other reasons. I may ask Arca and try one of their
120 backs to see for myself.
I had been unable to purchase my Horseman back locally
(Switzerland) because the local dealer had been unable to get
one in time from the European distributer. Instead I bought
at B&H in NYC. Now that I suspected my Horseman back to be
defective I decided not to try returning it to B&H because
of the shipping charges and the questionable outlook for
success. Instead, I decided to become a film flatness expert
by disassembling my film back, thereby probably voiding its
warranty.
In hindsight, I shouldn't have done that because after
some fiddling (I found that the pressure plate was not
parallel to the rest of the film back in its relaxed state
and I fixed that) the film still buckles the same 0.45 mm.
One thing that may contribute to the asymmetrical buckling
is that the cassette has a smaller radius "roller" on the
"right" side (the advance lever side) than on the left side.
I suspect the smaller radius bends the film harder so a
larger buckling force results.
I discussed it at Photokina with one of their staff. Needless
to say, he claimed there were no film flatness problems with
Horseman backs. He said I should send the film back back to B&H.
I told him if I would, I may well have to do without a film
back for two months and be no better off at the end.
Well, I were Horseman, I would not specify film flatness :-)
Somewhere on
http://www.smu.edu/~rmonagha/mf/flat.html
someone says that 220 backs are better because the film
is thinner than film & paper, but that's also anectotal.
I try to. My major reason to go with roll film was the ability
to bracket. I now expose my "center" exposure first.
Thanks. MF users, strictly speaking :-).
At this point, I am looking for alternatives. Mamiya makes
a 6 x 8 motorized back for the RB (cat. # 214-614) which
should fit on the same Arca Siwss adapter that I use for
my Horseman film back, if I interpret my Arca Swiss brochure
correctly. This time I will try before I buy.. 750 USD..
ouch.
Thanks
Frank
From Rollei Mailing List:
In the latest issue of Pop Photo they wrote about the new Zeiss film
flatness testing. Apparently, there is a new device that Zeiss developed
to check film flatness in cameras. Although Pop did not disclose much,
they did indicate that the test proved 220 film will sit flatter (2x
flatter) than 120. They also indicate that many customers complaints
about sharpness are attributable to film flatness problems in roll film
cameras, and more especially the length of time film sits in the camera
pressed around rollers. Most noticeable with photos taken with the lens
wide open.
I was wondering if anyone else has heard of anything that relates to these
findings?
From Rollei Mailing List:
....
I wonder just how much of a "breakthrough" this is. It seems to me that
measuring the contour of a flat surface can be done with a laser
interferometer with extreme accuracy. I think you cah check the film
plane, at least in the center, with a fairly simple autocollimator. It
would be interesting to know just what Zeiss came up with thats so new.
The problem of varying film plane in roll film cameras has been known,
it seems to me, forever. Even sheet film cameras can have trouble with
film buckling.
The trouble with popular magazines (not refering to Pop Photo
specifically) is that they can often report the invention of the wheel as
something brand new.
----
From Rollei Mailing List;
Kotsinadelis, Peter (Peter) wrote:
Sure. It was in CAMERA LENS NEWS, a Zeiss publication, and I have been
told that a fuller article will appear in INNOVATIONS, another Zeiss
publication (the successer to the ZEISS INFORMATION and JENA REVIEW
magazines).
CAMERA LENS NEWS is a freebie and all List Members are encouraged to
subscribe. Contact information is the editor, the noted Kornelius J
Fleischer at
Marc
msmall@roanoke.infi.net
From Hasselblad Mailing List:
A rather desperate-sounding FAQ and response from the Contax website
(sic):
Q. The RTS III [35 mm SLR] touts the vacuum back. Is there really any
benefit? (You realize, of course, that by making an assetion that the RTS
III is capable of making sharper prictures because of the vacuum system
you are saying that no other camera is capable of making photographs with
the same sharpness.)
A. The influence of the Real Time Vacuum (RTV) can be seen in
photographic enlargements. A scientific paper was prepared by Dr. Sugaya,
PhD., showing relative film flatness and its effect on sharpness. It was
noted that motor drives cause more film bend than manual advance cameras
and that the effect can be seen in enlargements, especailly when limited
depth of field is available, such as in macro photographic applications.
The influence of the Real Time Vacuum (RTV) can be seen in photographic
enlargements. A scientific paper was prepared by Dr. Sugaya, PhD., showing
relative film flatness and its effect on sharpness.
From Rollei Mailing List;
Peter,
If you want an in depth discussion of film flatness, give Bill Maxwell a
call. As I mentioned in messages in the last few weeks, he told me he has
been investigating this for quite some time. I believe he uses some sort
of columator or some kind of instrument which reads directly off the film
that's in the camera.
A brief summary of what I remember from speaking with him is that 35mm is
probably the least problematic, while roll film comes next, and sheet film
can really vary between bulging and flopping around in those holders. Of
roll film cameras, the magazine types with extreme turns in the film
transport are the worst, and straight across (like Mamiya rangefinders)
the best, with Rollei TLR's somewhere in between.
With roll films, he also believed the position in the roll was critical,
telling me that the first exposure on the roll was often the most off, or
buckled, with varying degrees of buckling in other positions on the roll.
My own experience of shooting a full roll at wide open of the same target
didn't give me any noticeable variances. I was just using a loop for
evaluation, and didn't have any scientific measuring devices.
There has also been much discussion of winding the roll film just before
the shot, and not ahead of time, to achieve maximum flatness. Mr. Maxwell
agreed strongly with this view and mentioned that he had come up with this
concept early on and passed it along to many folks. HTH!-Fred
Kotsinadelis, Peter (Peter) wrote:
From Rollei Mailing List:
-----Original Message-----
Jan wrote -
Amen.
In my 38 years of medium and large format photography film flatness had
never been a sharpness issue. It would take a pretty wrinkled film
surface to exceed the generous depth of focus provided by medium and large
format C of C's at even large apertures.
Jan's pointing to focusing as the likely culprit is consistent with my
experience. I once had a Mamiya twin lens that I thought had an error in
the lens-to-screen distance. There seemed to be a very slight focus
discrepancy between the screen and a ground glass at the film plane so I
mounted the camera securely to my workbench and positioned a dial
indicator on the lens panel. I focused diligently on a Siemen's star
about 20 feet away using a high quality 10 power lupe. I focussed and
focussed and focussed. Hah! You should have seen the range of
measurements. They were MUCH, MUCH greater than the backfocus error and
wandered all over the place (these focussing mechanisms don't exactly have
micrometer adjustments).
I ended up making oodles of measurements of both screen and film plane
distances and determined the final distances statistically. I found the
screen distance to be short by about .001" . . . MAYBE. At any rate, it
was meaningless in terms of application.
I have had trouble with film flatness in rollfilm holders for large format
cameras, though, revealing itself not so much as a sharpness loss but,
rather, as geometry distortion. The Calumets, in particular, are terrible
- significantly out of back focus as well, shifting focus towards infinity
(or, beyond!).
Even though Mannheim describes the film flatness problem test in his book
on the SL66, I've never had any trouble with my Rollei's, even in images
shot for 50 inch display prints.
Tim Ellestad
From Hasselblad Mailing List:
I think that Linhoff offers a 70mm vacuum back. Most aerial cameras can be
had with vacuum backs that use larger film sizes (5" rolls or bigger).
To be honest, I think that this feature would only be helpful if
a) you shoot 220 film - this assumes that the film you want to use is
available in 220.
b) you shoot at or near maximum aperture.
c) absolute sharpness is a major requirement.
What I mean by the last point is that a minor focussing discrepancy can
ruin
a whole day of aerial photography (incl. plane rental, etc), but may go
unnoticed in a portrait session.
I guess that I should add one more point,
d) you are unable to bracket your focusing on critical shots.
Again, this is an issue in a moving airplane, but not so much when you are
shooting a landscape from a tripod.
Bernard
From hasselblad Mailing List:
Both Linhof and Rollei makes 70 mm Vacuum Backs.
They are primarly intended for aerial photgraphy when you normally use
largest aperture.
I have tried my aerotechnica with and without vacuum and the shots taken
w/o vacuum was not useable. However, this was with 5 inch film.
I have shot several thousand negs with Hassy with 70mm back and 350/5,6
and 150/2,8 at largest aperture and have not noticed any difference in
sharpness when shooting several negs of same motiv. Hasselblad claimes
that their backs do not need vacuum due to the quality of the film
transport system .
Ragnar Hansen
Date: Thu Nov 02 2000
mboehk@my-deja.com wrote:
When my wife told me that she was going to buy some brushed
felt for her sewing and crafts, I had her buy some extra for
my 'scope. It cost $1.50 a yard (one-twelfth the price of
Protostar) and seems a lot blacker than paint.
sci.astro.amateur
Li0N_iN_0iL said. . . :
Felt is pressed fiber. It sheds. The ProtoStar paper is supposed to be
excellent for darkening, but difficult to install (from what I've heard).
--
Mark Wagner
sci.astro.amateur
htt://www.fpi-protostar.com
Ritesh
Paul Manoian
Date: Tue, 31 Oct 2000
Let me start by saying hello to everyone on the list, as I am new. I look
forward to learning much from this group. I have been shooting 35mm
seriously for 4 years and am looking to move into medium format. I have
several friends that have recently moved to the Contax 645 system. They
profess the virtues of the vacuum back on the camera which in theory sucks
the film flat while the shutter is open. The Contax literature implies
film in medium format cameras has a tendency to bow or curl thus resulting
in slightly soft images when shooting with a lens wide open. Can anyone
shed some light on this for me. Let me state I am not trying to incite a
series of Contax flames, I am only looking to make an informed decision
when I purchase a medium format system.
Thanks,
From Hasselblad Mailing List:
.... (see above post)
Film-flatness is indeed an issue. No need to criticise Contax for offering
a vacuum back at all. But it is an issue most of all when you want to use
your, fast, lenses wide open. Stopped down, depth of focus should suffice
to combat any ill effects due to uneven film positioning.
Zeiss recently said that, first of all, film flatness of 220 film is
better than of 120 film. Secondly, that flatness is influenced by a
combination of two factors: the particular way film is threaded in a film
back, and the length of time a film remains in a certain position in this
back, i.e. the time interval between subsequent exposures. Their
recommendations therefore are: use 220 film, and once your film is in the
back, expose it as quickly as possible. Five minutes between exposures is
the maximum time one should allow.
Hasselblad backs, with their "double bend" system (the film is bent
against its curve, doubling back over two rollers either side of the
frame), and any other backs that use this system, are particularly prone
to film unevenness.Cameras like the Pentax 67 use the 35 mm style straight
film path, and have better evenness.
However, film flatness is not that big an issue: it is perfectly feasible
to get good results even without a vacuum back, and with the double bend
film path.
From Hasselblad Mailing List:
Mike,
Linhof has vacuum backs (probably for aerial
cameras), Rollei has an outrageously expensive back
for their 600x model, and possibly Beattie has a long
roll back that might be worth investigating but I'm
not sure if it is vacuum. The Beattie long roll back
is powered by a car battery or an AC outlet if I'm not
mistaken.
[Ed. note: Thanks for this great tip!!]
Hiya Bob,
Have you seen the article on rollfilm flatness in this
summer's edition (no 10) of Zeiss's Camera Lens News?
Go to
http://www.zeiss.de/de/photo/home_e.nsf/allBySubject/Launch+-+Zeiss-engl+JavaNavigator
Later,
Owl
Dr John Owlett
From Bronica Mailing List;
In my opinion film flatness is well down the list of causes of less than
optimal sharpness. I feel that it is blamed just because it is something
that the advertising people can exploit. Our new improved model has much
better film flatness... and so on. The significant causes of less than
optimal sharpness as I see them are (concentrating on the Bronica MF
SLRs):
1) Camera movement. If you hand hold then forget film flatness issues.
Out of interest I wanted to see what the Bronica lenses could do. Using
my EC I did some shots on my Manfrotto tripod using MLU. OK so then I
mounted the tripod head onto a heavy engineers vice and repeated the shots
again with MLU. The shots were sharper. OK so now we mount the camera to
a heavy aluminium angle (6mm thick). Clamp this in the engineers vice and
take some shots with MLU. Again the images are sharper. So now we bolt
the camera onto the aluminium angle using BOTH tripod screw holes (for
those unaware the EC has two tripod holes a 1/4" and a 3/8"). Again
clamped in the vice and again using MLU. Gee the shots are sharper again.
So are we still saying film flatness is an issue??
BTW for the above tests I use a pocket microscope to ensure optimal focus.
2) Focus error. Some time ago I did a calculation as to the focussing
accuracy for an SLR using the standard viewfinder. The results said that
the accuracy was only just inside the DOF at maximum aperature. To verify
this I have asked several keen photographers to repeatedly focus on the
same object. Sure enough a person with average eyesight has a spread of
focus settings a little inside the DOF markings.
For MF the circle of confusion is about 1/20 mm. I have not done the
calculations to see what Nikon used for the DOF scales on their lenses. So
we can focus just inside the DOF at maximum aperature. Taking the f/2.8
of the standard lens and some simple trigonometry. The focussing accuracy
in term of lens position relative to the film will be +/- 1/8 mm, yes 1/8
mm. With slower lenses this will be worse.
Are we still claiming film flatness is an issue??
The focus accuracy will be true for all SLRs unless some type of high
magnification device is used. For most of my lens tests I use a pocket
microscope which gives x30 magnification.
Some historical perspective is required here.
First the current 120 film is a very different beast from the original 120
film. There have been significant improvements in the film base as well
as the application of an emulsion on the base. The tollerances on the
film are far more exact than the camera.
Yes at the time 120 would have been seen as an amateur film, but we must
also remember that back then 120 film was MINATURE film. So the status
would be like 110 film today. This does not mean that the film was of
lesser quality, just that the size of the negative was small.
Advertising hype again. Digitial is great if you are in a studio where it
can be piped straight into a computer. But if we are out and about... A
scan resolution of 2000 dpi 24 bit colour is a resonable scan. With a 6x6
negative (58 by 58mm) we have close to 60M. So a 120 roll of film holds
720M of info. Which would you rather carry a pro pack of 120 or a 3.6Gig
hard drive!!
Richard Urmonas
From Rollei Mailing List:
Hi All
Every now and again I get to wunderin
My Granma's 120 rollfilm camera had a fixed lens and a
curved film plane. Considering that with today's
technology making an accurate curved film plane would be cake,
would there be any advantage to producing lenses, particularly
wide angle ones designed for curved film planes? What's the difference
between
lenses designed for flat Vs curved film planes? I realize that
the film plane curvature would have to vary with focal length,
so we might need interchangable film planes as well.
Also, film flatness on a curved film plane can be acheived
without a pressure plate as long as there isn't too much
tension on the film.
Javier
From Rollei Mailing List:
The Minox Complan 1:3.5/15mm lens, basically a Tessar design, is the
most prominent sample of a lens designed for a curved film "plane". Its
predecessor even had a fifth real element actually touching the film!
This set-up was very prone to scratches. End of the 1960s the Complan
was replaced by the current design with a flat film plane. However, the
Complan lens is still considered to be superior in optical performance.
See http://www.slonet.org/~dkrehbie/minox/mnlens.htm
Regarding film flatness, the Minox already has an advantage in terms of
a thick film base in relation to negative size. In addition, the film
pressure plate is connected with the film advancing gear. When the
camera is ready for shooting, the plate is pressed against the film. For
advancing the film, the plate is retracted.
Hans-Peter
From Hasselblad Mailing List:
My biggest problem with TechPan film is that it is too thin to stay flat
at the film plane in a Hassi magazine. Probably best in a Pentax 6X7.
Rich
From Hasselblad Mailing List;
I would wonder why anyone would buy a Polaroid scanner when a Minolta unit
that will do 120 can be had now for around $2,000?
Also, I have tested many of the Hasselblad lenses and have always found
that the weakest link in the chain as far as sharp photos are concerned is
the Hasselblad magazine. With normal resolution Pos and neg films most
Hasselblad lenses resolve past the films range. With thin-base high
resolution films such as velvia and especially with a film such as the
estar based tech-pan the film plane flatness provided by the Hassi mag
precludes super-high resolution. One would have to want an apocromatic
lens more for its image rendition characteristics such as contrast etc.
Rich
From Contax Mailing List;
Some info about the vacuum system on the RTS III.
The pressure plate pushes against a set of outer rails and leaves 0.175mm
of gap for the film to travel between the pressure plate and the inner
rails.
I measured the Aria also, and it too has 0.175mm of distance between the
pressure plate and the inner rails for the film to 'travel'.
The vacuum area of the pressure plate only is in the center of the
film...(which leaves me with questions about the edge flatness...since it
appears it does nothing for it).
Here are some film thickness measurements:
These measurements show the film may have as much as 0.040mm 'play'
between the pressure plate and the inner rails.
Anyone know of any articles dealing with the 'advantages' this vacuum
system is supposed to achieve? How about articles on the detriment of
film (not) flatness?
Off to shoot a roll and see just how heavy this camera is ;-)
Date: Wed, 10 Jan 2001
Hi Roy;
The reason most people believe that the best resolution for large
format lenses occurs at f/22 is due to the film flatness problem and maybe
also field flatness that reduces resolution out towards the edges of the
field.
In the testing that I did the aerial image was definitely much
worse at f/22 than at f/16 for all of my lenses, even at the edges. I did
not post the numbers to attest to the obtainable resolution, but to show
that at f/11 even large format lenses are close to the diffraction limit
in the center of the field. By f/16 and f/22 diffraction is the limiting
element.
Medium format lenses will not have substantially greater
resolution at these f/stops - they can't. They (hopefully) will have
better contrast and resolution at f/11 and larger. I just received my new
microscope ocular today so as soon as I find a couple of free afternoons
I'll go back to testing my lenses again (to include my 35mm and 6x7
lenses).
The depth of focus is a non-issue as far as sharpness is
concerned. Maximum sharpness occurs at a single plane, any deviation from
that plane reduces resolution - the "circle of confusion" needs to be
added on top of the lens's own limiting aberrations. Of course I can't
swear that roll film is flatter, the ideal would be a sheet film vacuum
back - wish I had the money (maybe I'll call Mr. Hoffman).
Once I get done
messing around I might adapt my Pentax67 to the back of my view camera and
get some "real world" numbers. But then I would have to choose between 120
and 220 film - it never ends. Besides, absolute sharpness only really
matters if you're shooting 2-dimensional objects - otherwise contrast is
the factor that has a greater influence on our perception of sharpness
(within reason).
Cheers,
...
From Rollei Mailing List:
you wrote:
snipping...
The only adjustment is the conincedence of the viewing lens to the
taking lens. However, some people feel it should be offset slightly from
the infinity position as indicated by a ground glass in the film gate on
the premise that the film buckles just a little and does not lie exactly
on the assumed film plane. Is this true? I don't know but it could be
determined by using an autocollimator with film in the camera.
One could also argue that such an offset could also help compensate for
curvature of field, but the lenses used in Rollei cameras, even the
relatively low cost Triotar, have little curvature of field. I am not
convinced there is enough film buckling, or that it is consistent enough
to really justify offsetting the focus.
----
From Contax Mailing List:
Hi Austin,
That can be obtained from film data sheets. I list a few:
Print film:
Fuji NPC: 122um
Slide film:
Agfa RSX II 100: 120umB
Note: um = 10e-6 m. 120um = 0.120mm
Tom
From Contax Mailing List:
Austin Franklin wrote:
The various film thicknesses that passed in review on this list during the
past week differ from 0.15 mm by a maximum of 0.03 mm. This is less
than the depth of focus of an f/1.4 lens at full aperture. Add to that the
focussing uncertainty, and I don't think that you have anything to worry
about. That is, if the RTV works (which I don't doubt) and if the optical
path is properly adjusted.
P.
From Contax Mailing List;
....(see above quoted) I do not know if what you say is true or
not, but according to Ben (who says according to Kyocera ;-):
"Kyocera has stated that a deviation of just 10 microns, let alone 65u,
would produce a 1cm deviation in background focus of a portrait taken at
3m using a Planar 85/f1.4."
First I wanted to get the issue that the film plane changes with film
thickness out of the way, and now I'll figure out if that matters at all.
From Nikon Mailing List:
I buy fast lenses so I can shoot slower and cheaper
film. ISO 100 film is often a dollar or more cheaper
per roll and sharper and finer grained. The fast
glass saves me film money, while the slower glass
costs me more in the long run since I have to buy
faster film. Does this make sense?
From Rollei Mailing List:
you wrote:
I thought of this too but I am not sure just what the film does in the
gate. An auto collimator would be able to dermine exact focus because you
could see the image on the film. It would be interesting to know just how
far from flat film is in a Rollei gate and how its immediate history
(whether its just been wound or has sat there for a time) affects the
flatness.
Its obvous that the film can not buckle inward, the question in my mind
is whether it really does belly out or if that is just intuitive.
----
From Rollei Mailing List:
Date: Wed, 7 Feb 2001
... (quoting above)
When first attempting this I spoke with several repair techs and all
agreed the filml would buckle a bit and all were of the opinion that it
would be toward the lens. One Rollei repair person told me of a device
they used to collimate TLRs at the factory which actually accounted for
the not so perfect film flatness. Wish I could remember the name.
Personally the way the Rollei winds film, if its been sitting awhile there
would even be a more pronounced buckle of the film at a particular spot
where it layed across the rollers before it came to the frame.
Lack of bending the film is part of the Rollei 6000 series backs which
probably provides better film flatness than older TLRs do.
Peter K
From: flexaret2@aol.com (FLEXARET2)
I have never owned a Hasselblad, but have employed photographers who have
used them and gotten us excellent results. They have a great system and
make top equipment. I have their current lens catalogue and their optics
are second to none. If I had unlimited money to spend on photography I
would buy their latest focal plane shutter model and some of their
incredible lenses. I have examined one of these cameras at a recent expo
with a Zeiss 100MM f2 lens and I thought this was an amazing outfit. I do
appreciate the precision manufacture of their equipment and if I had a
project which needed it and could pay for it I would certainly buy it.
However, for my purposes I have been using older Bronica S2A type cameras
with focal plane shutters which allow adapting a wide range of lenses. I
did a precision adaptation of a Zeiss 180MM f2.8 Sonnar to Bronica S2A to
take sharp portraits while blurring out the background and using the lens
wide open. As I could not get sharp enough photos, I went into examining
the camera as the problem and had to calibrate the finder groundglass as
an improvement. I then found that I had a film flatness problem in the
backs. I went into a study of this and improved the film flatness until I
could get the sharp results I had anticipated from that 180MM lens and
others.
My study of film flatness led me to find out that this problem did exist
with large format film and to a lesser degree with medium format and even
lesser to 35MM. It stunned me to also find out that focus shift affected
the final results. Focusing wide open and then stopping down to f11 and
the image is defocused from where I had set the focus. I always check
focusing with stoppping the lens down if at all posssible before shooting.
I was amazed to think that I could not easily shoot at all apertures on
120 and get the focus I had set. Further research revealed that this was a
general problem with all brands of especially medium format equipment and
was a problem for critical work. That is why in scientific applications
glass plates are used and not film.
By bringing up this subject in a forum like this it is my hope that the
following may happen:
1- People will become aware of this problem and spread the word around to
seek solutions to it.
2- Kodak and other film manufacturers will research a way to improve the
100 year old (formerly amateur only) 120 film base to minimize these
problems.
3- Equipment manufacturers (as Kyocera/Contax has done) will publicly
recognize the problem and improve their backs/equipment to
minmimize/eliminate the problem. There is no reason Hassy can't improve
their backs and make a new model back which will then fit all existing
cameras.
There is extensive research and information about these film flatness
issues at Bob Monaghan's excellent Bronica and Medium format Mega Site-
http://www.smu.edu/~rmonagha/bronica.html
(He uses Hassy and Bronica - both old and new).
From Rollei Mailing List:
Neil
Yes, I have found that the glass plate does
****-all with a Rolleiwide or 75/80mm
lens, but is effective with the Tele-Rollei
only.
It is an exercise in futility to use it other
than with the Tele-R'flex.
Jerry
...
From Rollei Mailing List:
you wrote:
At least one type of autocollimator was available for setting infinity
focus. A flat mirror was placed against the film rails of the gate. I
suppose some research must have been done on what the film does in the
gate, but I can't cite any thats specific to other than aeial cameras or
motion picture cameras.
The film can not bend toward the gate, if its bends it must bend toward
the lens. Roll film tends to cup so that it is convex toward the emulsion
side. This does not mean that the combination of film and paper backing
could not become concave toward the lens. Its the sort of thing where
intuition can be wrong. However it would seem that the elastic forces of
both film and backing paper would tend to push the film against the
pressure plate rather than toward the lens.
----
From Rollei Mailing List:
I cannot speak directly for the Rollei's as it is not possible to examine
the film without special optical devices. However the Kowa MF SLRs have a
film path very similar to that of a TLR and here it is possible to examine
the film. In the Kowa the film is very flat. I was not able to detect
enough bowing in the film to see which way it bows. Looking at other
cameras such as a Mamiya Press which has a very straight film path there
is a small amount of bowing towards the lens.
Estimating the amount of bowing is best done by using the camera itself.
I have found that with careful focus I can resolve over 100 lines/mm at
f/2.8.
This would require the film to be flat to less than 0.03mm.
Richard.
Richard Urmonas
From Rollei Mailing List:
On the Tele-Rollei I can see the change in focus between the glass being
fitted and not fitted. The difference is small (well within normal focus
tollerance).
I personally find the glass plate adds a "halation" type of effect and
prefer not to use it for this reason.
Richard.
From Rollei Mailing List:
you wrote:
How thick is the glass plate used in the Rollei? The glass will extend
the light path by the thickness of the glass times the ratio of the index
of the glass over air, about 1/3rd the glass thickness for average glass.
I don't know how, or if Rollei compensates for this. It may not be
necessary if the glass is thin enough, otherwise, the glass itself may
accound for the difference in focus.
----
From Nikon MF Mailing List:
I looked into buying these, but the needed minimum custom order size to
get
makers (Beattie etc.) to setup to make some messraster screens (vs student
budget) precluded doing so. The screen is precision ground in two planes,
slightly offset from each other (e.g., micron width lines to same depth on
an optically flat screen surface). The whole surface of the screen acts so
the subject snaps into focus, but only when the exact mid-screen focusing
point is reached. Otherwise, one half or the other is closer to the focus
plane, but the whole screen is not sharp (but easy to see it getting
better as approach precise in-focus position). Sort of like the slash
line in a rangefinder, but the focusing offset is on the entire screen,
so you can see when subject snaps into position (versus one line in RF).
Great idea, patented and fielded, but it is so good that it reveals the
flaws in the rest of the system, particularly film flatness errors. So you
would need a camera with very good to great film flatness to exploit this
technology. Even mass produced, the cost would be more than typical
beattie bright screen type screens ;-( Moreover, you would need to have a
tech precisely align the screen to the camera's film plane to get optimal
results as part of the installation process. Most interchangeable screen
and lens registration distances are not precise enough, so this would be
custom installed in each camera and given the cost, stay there.
On the plus side, you could see 15-25% improvements in resolution and
easier precise focusing with every shot for the one time cost; since most
lenses are not used to full effect due to modest focusing errors and film
flatness and other system alignment issues. This would be much cheaper
than getting better lenses (e.g., Zeiss, Leica) with higher resolution
figures and hand aligned elements etc. see
http://www.anstendig.org/AutofocusFlaw.html on messraster and patents
the current trend is away from precise focusing, esp. using autofocus,
which is limiting us to about 55 lpmm maximum focusing accuracy
consistently
(See http://www.smu.edu/~rmonagha/third/af.html) and color print films
and the like which limit us to this 50-ish lpmm range (see limits page at
http://www.smu.edu/~rmonagha/mf/limits.html) There is no sense having an
optical focusing system that lifts you from 80 lpmm to 100+ lpmm from
your nikkors if the film bulges out of flat focal plane position needed
etc.
===================
on a related matter, I see the new N1 contax offers "autofocus
bracketing"; by which they automatically take three shots at various focus
points, when you select this standard mode, to help ensure that you get at
least one autofocus photo in correct focus, near or on the desired subject
- example being leaves on vine - do you want the center of mass? the first
leaf in focus, rest behind out of focus more and more, or do you want the
trellis in sharp focus and the vines more blurry soft focus image? Since
you can't control many AF sensor positioning setups to select which of
these you want, you now have the option of blowing three shots to get one
you want. Or you could just use a manual focus camera ;-) ;-)
grins bobm
[Ed. note: Special Thanks! to Mark Anstendig for supplying this followup
information on the Messraster - esp. patent cites!]
I am sorry this never got sent. things have been hectic.
If it was sent, I have added the patent info here. if not, I hope it
still is usefull to you.
The inventor himself made them by hand. With great trouble to attain
the necssary precision, back then. Today that level of precision is
not so daunting.
Beattie was interested and was going to make a few for me, but
decided not to. It was not worth their while making jut a few, and
they evidently did not want to risk making a production. their chief
technician knows the data and enough to make one.
The possibility of making a screen by dividing the surface in half,
caddy-corner down the middle is possible. It would, however limit the
ability to focus anywhere on the screen.Dahl made some in the form of
a central circle divided in half, much like a through-the-lens
range-finder, but , of course, it functioned the way a messraster
functions. But first focusing and then framing changes the focus, the
that screen usually does not result in a good end results.
I found the patents.
the first US patent was May 30, 1944, # 2,350,151
For "Optical Focusing System".
The second is August 30, 1966, # 3,269,292
for "Fine Focusing Device".
Another # 2,286,471 is mentioned in the second patent.
I hope this helps.
Mark
PS Let me know if you do anything with the messraster. I might be
interested myself.
...
From: flexaret2@aol.com (FLEXARET2)
Since most photographers shoot subjects that are not perfectly flat -
people, scenics, buildings, products etc. - the lack of perfectly flat
film is not always obvious.
However, it is always good to shoot several shots of an important subject
as the film may be rippled in a different place from shot to shot.
Regarding the Contax 645 vacuum back it only works with 220, which is film
negative itself and no backing paper. It will not hold 120 film flat as
that film is a sandwich of negative and backing paper.
Anybody wishing to test the film flatness issue with a medium format
camera with interchangeable backs, that can wind off the camera - try the
following-
Put a roll of 120 or 220 film in a back (off the camera) with the dark
slide removed. Then wind from frame to frame (you may have to unlock the
lock with a small screwdriver or such to wind to the next frame). Then
examine the film in the aperture for how flat it is lying against the
pressure plate. Look also for any rippling pattern across the face of the
film. This same test can be done with medium format cameras with no backs
(Exakta 66 and Pentax 67 etc.) in which you can remove the lens. Set the
shutter to B- open the shutter and hold it open - maybe with a locking
cable release- and with a roll of film loaded. Carefully(!!) probe into
the film in the aperture with a pen or blunt object - be very careful not
to release the shutter and mirror and foul up your camera.
This is the test that technicians use to check film flatness.
You will notice film rippling varying from frame to frame, camera to
camera etc. Or little or no film rippling and unflatness. It would be
interesting to know which modern cameras have very little of this problem
today. You can make your own conclusions as to how bad this is or if it is
no problem at all.
It would be interesting to read various test results from owners of
different medium format camera brands.
[Ed. note: Mr. Meyers is the author of numerous photography articles
in many noted photography magazines (Modern, Pop..)]
One fact is not mentioned in the 25mm/24mm lens saga. That is...
different cameras will give different results with the same
lens (if you could fit the same lens on them).
Par example: one of the features of the old-fashion Contarex
is its superb film plane. It actually stabilize s the film
during exposure, keeping it as flat as possible in the
correct channel without the need of a vacuum system.
In the need to make camaeras smaller, film holding and
channeling features are often eliminated.
The same lens on all the cameras would tell you this.
But for now we can only compare lens and camera systems
if we want a fair comparision. Just my thoughts on the matter.
Please correct me if you think I'm wrong.
Ed
From: "Christopher M Perez" christopher.m.perez@tek.com
LoveThePenguin wrote
...
I found the difference between all my holders to be 0.11mm (0.0043
inches!). That's not bad at all. I have 120 cameras that bow more than
this! So I'd say buy a stack of identical 4x5 film holders (newer the
better), measure them in your camera back and check their alignment.
Choose the most consistant, use them, and sell the rest.
Dial indicators are wonderful things... :-)
- Chris
From Medium Format Digest:
I recently wanted to see if mirror lockup (MLU) on a Bronica GS-1
would improve sharpness appreciably. I set the camera on a tripod,
and fired of 3 shots, the first without MLU, and the second two with.
What I actually found was that the influence of MLU was irrelevant
compared to sharpness problems caused by a lack of film flatness. On
the first shot, one half of the image was sharp, the other not. The
next image, same result, but different halves of the image were
affected - and very noticeably too. The final shot was a sort of
compromise; pretty good all over, but not as sharp anywhere as the
sharpest bits of the previous two images.
The shots were 8, 9 and 10 from a 120 film left overnight in the
camera (Provia 100F).
This leads to a couple of conclusions. From what I have seen, the
lenses on the GS-1 are very sharp - but let down by the film flatness
problems. The problem itself is how the film is wound over rollers,
causing it to bulge up from the film plane when wound on. Some
cameras fare better than others, eg rangefinders, because they do not
fold the film back on itself over rollers. I now have an explanation
for a number of unsharp shots taken over the last few months. The
worry is: how to tell when it will happen again?
Carl Zeiss have a very interesting article on this subject entitled
"Is rollfilm 220 better than 120 in terms of film flatness?" You can
find it at
http://www.zeiss.de/de/photo/home_e.nsf/allBySubject/Launch+-+Zeiss-engl+JavaNavigator
Look for the archives, volume 10.
Looks like using 220 film reduces the problem.
Anyone else suffered from this?
--
From Medium Format Mailing List:
Quentin,
I have know about this film flatness 120/220 problem for a long time.
However, when I recently adapted a 180MM f2.8 Sonnar to Bronica S2A - I
wanted to use it wide open at f2.8 for portraits reasonably closeup-
keeping the eyes sharp and blurring out the background.
That is when my study of old Bronicas and other 6x6cm cameras, led me to
align the focusing screen on 3 Bronicas, write some articles and further
deal with film flatness problems in the backs.
Last year I went to the Photo Plus Expo in New York and examined all the
new 120/220 cameras inside, to see how film flatness was being dealt with.
Some put spring drag on the supply roll to keep the film more taut
(Hasselbland and some others). Others (Rolleiflex, Pentax 67) had a
straight across film plane.
If you take the back off your camer you may be able to see if the film is
flat or not by removing the slide, if you can still roll the film through.
Then you might experiment with ways of keeping the film flat.
The problem with the spring tension idea as in Hassy that it puts too much
drag on the film and wears on the wind gears. The old Koni Omega had a
retracting pressure plate which clamped down on the film in the gate.
You may be inventive and find a method - as I have done with the older
cameras.
- Sam Sherman
...
From Rollei Mailing List:
J Patric Dahlén at jenspatricdahlen@hotmail.com wrote:
I have a Suydam rollfilm adapter back for my old Annivesary 4x5, and it
most certainly does give a nice, pleasing, round bulge to what should be a
flat surface. :-) And it's an unsymetrical bulge, too. :-) Maybe I will
be able to compensate by sticking a piece of rolled glass in front of the
Ektar. :-)
pk
From Rollei Mailing List;
Emmanuel,
... but on the other hand, in the case of Rollei TLRs with flat glass
provision, visibly improves image quality by ensuring the film is FLAT,
not a more or less bent surface.
Rollei took account for the altered image position - you can see that
the glass protrudes from the original film channel (and therefore a
dedicated back is needed). Thats how I found out that any element in the
light path has an effect.
Sven Keller
From Rollei Mailing List;
... but it certainly was a cost saving also.
I have the flat glass provision on two of my cameras but only one glass
and I tend to have films in more than one camera at a time and pick the
one that I feel like using.
The way it is some films stay in a camera quite a while and this makes
the film flatness issue worse. One of the Rollei rules I have learned
somewhen is that if you want best film flatness you should advance the
film right before the shot, not after.
I *see* out-of-focus concerns (which I *believe* to be caused by film
bulging) sometimes on the camera without the glass whereas I have not
been able to *see* a degradation in other aspects of image quality when
using the glass.
I know and will always admit that this is very subjective, but then, not
more subjective than judging the effect of an UV filter. As for the theory
behind it, you are perfectly right, as far as I understand it. To have
optimum optical correction the lens would have to be designed with the
glass in mind or the glass would need to be a lens itself.
Sven Keller
From Rollei Mailing List:
Degradation at f2.8 is usually either a paper backing or a film
tensioning problem, inherent in the 120 roll film design. Avoid shooting
at f2.8 for the first 2 exposures and the last two exposure. Not
definitive, but a good rule of thumb.
My initial combination was an SLX back on a 6006 body, great light
weight combo. I think that the 6003 design is better thought out for
daily hand use. Whereas the 6008, a three brick taped together design,
is better suited for the studio.
Slobodan Dimitrov
From: sapasap@aol.com (SAPasap)
When I used to shoot with a 2.8F 12/24, I did notice that changing from
120 to 220 roll designation did not seem to change the pressure plate
altitude at all.
I asked this question of a camera tech, and his comment was that
performing this switch in the Rolleiflex does not change spring tension or
plate elevation-- it just changes the film counter.
Since I'm not a tech, I cannot confirm this is the case, but this did not
make me happy, and he agreed.
Also, I think some years back you were able to change the previous 12-only
models to 12/24 models... what you ended up doing was somehow resetting
the film counter once 12 exposures were hit... and then either starting
over again for another 12, or else counting down from 12 to 0. I forget,
since I never used it.
Some would call that mickey mouse, I think it's ingenious. A way of
extending a basic camera to do things it was not designed to. For
example, anyone remember the Rolleiflex motor drive unit... a box with a
crank that comes out and spins the film advance lever on the camera, after
another linkage trips the shutter?
From hasselblad mailing list:
Robert Meier wrote:
There are very fine sheet film holders that overcome these problems, like
the Sinar precision sheet film holder cat.no. 566.36, maximum deviation
from flatness: +/- 0.03 mm, or 1/800".
From Hasselblad Mailing List:
Yes, that's true. But with a standard 4x5 holder, a Lisco, for example,
the film can wander around a lot.
From hasselblad mailing list;
...
Ever tried double sided sticky tape?
Seriously, Sinar also offers adhesive backs in 5x7" and 8x10" (cat.no.
566.37 and 566.38): you don't slide the film in anymore (it wouldn't slide
very well across a sticky surface ;-)) but place it against a
self-adhesive back. No more wandering film, no bulging, very flat.
They offer replacement self-adhesive sheets, good for several hundreds
sticky reloads, so maybe you can craft your own?
From hasselblad mailing list:
I found it right here:
http://www.sinarbron.com/filmholders.htm
Mark Rabiner
From Hasselblad Mailing List;
I´ve been using my blad for astrophotographic work for years now. I
think it´s one of the best methods of testing a camera because of the
star images which should by ideal points on the film. The blad and
especially the Zeiss lenses are really great, except of one thing: the
film flatness. Many negatives are influenced by this phenomena. Star
images are no longer points but large bubbles. In astrophotography this
is nothing new and even 35mm SLRs have problems with the film flatness.
When analysing the negatives I found a zone, normal to the direction of
the film, that shows a deviation of film flatness up to 0,4mm. Humidity
has also an impact on the film´s buckling. I measured deviations of up
to 0,7mm.
For use in astrophotography film flatness is of great importance, but
what about other fields of photography? What are your experiences?
To eliminate problems with insufficient film flatness I designed a
"vacuum-magazine" (a modified A12). At present I´m thinking about offering
this system on the market.
(Of course, when using film120 the paper back has to be removed to gain
the effect.). What do you think about it? Any comments?
Thanks in advance.
Peter
From Hasselblad Mailing List:
When I need better than roll film film flatness (which is not very often,)
I use my Hasselblad cut film back and cut film holders. Sheet film is flat
and the way it loads into the Hasselblad holders makes it pretty flat.
Except for a few very specialized photography tasks, there isn't much that
really needs absolute film flatness. I'm not sure if there is much of a
market for a vacuum-magazine.
Jim
...
[Ed. Note: since cut film is one way to get around film flatness problems
on some systems, here is some related info...]
Here is a digest of answers and personal idea I posted to the list on
this subject; sorry for those of you already experts about his stuff.
-------------
-----Thu, 2 Nov 2000
Remains the question of matte black finish. Anodising alumin(i)um is
probably he best. For brass, a simple blackening process (based on hot
ammonia/copper sulfate) exists but is actualy not easy to do at home.
Black matte paint is supplied by various photo suppliers. Tetenal has
some on catalog.
-------------------
for cutting film : the *length* of 3.5" is *the most* important
(clamps) ; width can be smaller than 2.5", e.g. 2"1/4.
6.5 X 9 sheet film is available at least as:
- AGFAPAN 100 B&W,
To process 6.5x9 sheet film I use my basic Paterson 135/120 daylight
tank without spiral (2 sheets, back-to-back). You can use a Jobo drum
processing machine with the special spiral sheet film holder. Or the
simple COMBI-PLAN rectangular daylight tank.
-- Emmanuel BIGLER
From Hasselblad Mailing List:
I like the work with the blad and I wanted to modify the existing backs
with a vacuum system so that I can use them for my purposes. Large Format
is indeed a very nice thing. But even when using sheet film, you have to
use a vacuum system or, as O.G. mentioned, an adhesive sheet film holder.
The reason: even sheet film starts to bump out when it is exposed to
humidity, what is normally the case in astrophotography.
Frank Lew schrieb:
....
From hasselblad mailing list;
Hi,
I've heard some discusion of film flatness problems and Hasseblad backs.
Just for the heck of it I took a the dark slide off a back and advanced
the film a frame. As the film was advanced one could see a wrinkle where
it had been wrapped around the roller. Pushing my finger against the
wrinkle visible flattened it.
The film was sitting in the mag for about five days. Is it a good idea to
skip a frame once the film has been siting in the mag for awhile? How
long is a while?
A little disapointed,
Jeff
From Hasselblad Mailing List;
Jeffrey Muehl wrote:
Yes, probably.
According to Zeiss' tests, a while is 15 minutes (wrinkles are probable)
up to 2 hours (wrinkles are certain to appear), depending on film and back
used. They recommend a maximum interval of only 5 minutes between
exposures.
But have you ever noticed any ill effects due to film uneveness?
From Rollei Mailing List;
The glass back was standard issue on the Tele Rollei and the Rollei Wide.
For other cameras it was an option. By serial number 3.5F cameras taking
the optical flat glass back are from 2230000 to 2815050. The 2.8F cameras
that were capable of accepting the optical flat glass back are 2400000 to
2451850.
The option was withdrawn because it was found that the glass could
potentially (and did) trap dirt between the glass and the film and thus
was not particularly popular.
The pressure plate has an extra tab on it. When the back is closed, this
tab presses on a pin embedded in the camera. The purpose of this pin is to
release the pressure plate when the optical glass is in the film gate,
otherwise the film would be clamped between the glass and the pressure
plate. The hump accommodates a mechanism that allows the pressure plate to
evenly release and put pressure on the film and glass when the film is
cranked through.
todd
Austin Franklin wrote:
From Hasselblad Mailing List;
More film types are available in 120. 220 typically is flatter.
For me, I like 120 simply because I can buzz off a roll in nothing
flat...but when I shoot 220, I always end up with a roll in the back, and
I'd prefer to leave film in a Hasselblad back, it tends to form to the
rollers, and one frame can get "distorted".
It depends on what I'm shooting...and if I'm using development
compensation or not too...since you have to shoot the entire roll with the
same compensation.
[Ed. note: vacuum back for contax 645...]
I recently bought a Contax 645 system. I had rented one on two separate
two week fashion catalog shoots and fell in love: Great lenses, bokeh,
handling etc. Sold my Hasselblads to buy it.
The Fashion studio I work in has a Mamiya 645 AF with a LightPhase
digital back, and I find the handling of the Contax far superior.
However(!), the first group shot I did with my 45mm@f8 had softness on the
left side, which led to a series of sharpness tests and a trip to Kyocera
of the whole kit. They adjusted the flange back on my film back, claimed
to have sharp test film and sent it back. I shot more test film with same
softness, horrible wide open, getting better about f8-11 with both 45mm
and 80mm. Kyocera sent me another back to try, with a 220 vacuum insert as
well as the standard. The vacuum one is better, but still not what I
expected from this camera. In fact, at the risk of offending this list,
the Mamiya blew it away at matching f stops and 120 transparency film.
I went back to the dealer and tried their camera setup: Looks like my
camera.
My question for the list: Should I just return it, or try to fix it?
Idea what it is? Both the dealer and Contax have been great: I think
they will do whatever it takes.
Thanks!
Randy Boverman
[Ed. note: Exerpt from noted Leicaphile and camera and lens tester and
author Erwin Puts on film flatness...]
....(on film selection)
Now the film flatness issue.
In the previous post I noted that the only fixed dimensions are the focal
plane of the lens (relative to the flange) and the film guide rail
distances from the flange (the film channel). The focal plane, that is
obvious, is located inside the film channel ( in the Leica case 0.05mm
inside the film channel (measured from the flange).
Ideally the film emulsion should be at that same position.
In the classical Rolleiflex you could insert a glass plate in front of
the film emulsion that held the film flat and in a location such that
the front of the film emulsion would coincide with the exact focal
plane of the lens.
In a 35mm situation you can not do it. So the film lies somewhat loose
inside the channel, the back pressed on by the pressure plate and the
perforation sides are limited in their forward extension (to the lens)
by the guide rails. The natural tendency of the film is to curl away
from the lens, but all studies will tell you that in practice a film
emulsion at the film gate will bow outwards (towards the lens). The
center of the film area will be closer to the lens than the outsides.
So if I use a Techpan with a total thickness of 103 micron (0.0103mm)
(base 100 micron, emulsion 3 micron), the pressure plate will ensure
that the front of the emulsion is at least 103 micron towards the focal
plane which is in this case located at a distance of 150 micron from the
pressure plate (assuming a zero tolerance for simplicity). Some outward
bulging then will guarantee that the emulsion will be in a location of
the focal plane. A thicker film with a thicker emulsion layer will have
the focal plane in the middle of the emulsion, but these differences do
not matter at all.
Now what are the measurements to try to capture this bulging of the film
towards the lens.
Kyocera, when introducing the RTS III and the vacuum back stated that
they had found following figures. A true flat film (with their vacuum
mechanism) would still deviate at most 10 micron from the ideal position
and films without vacuum plate would deviate 20 to 30 micron from the
plane position.
Adding the 30 micron that Kyocera found to the 103 micron of the TP
gives 133 micron which is very close to the ideal location of the focal
plane.
The APX25 has a total thickness of 123 micron and with bulge it would be
153, so exact where the focal plane should be.
The focus depth we discussed earlier for a 1.4 lens is 47 micron (in
both directions). So this depth would cover the small deviations in film
bulging.
The Kyocera figures are not alone. Zeiss did their own analysis and
noted that film could deviate by 80 microns, which introduced in the
Planar 1,4/50 a contrast from from 60% to 20%!!
Goldberg studied a large number of SLR's and found that the difference
between focal plane and film plane (including curvature of the film
surface) averaged 70 micron, with extremes to 170 micron. IN such a case
the focus depth would not cover any errors. But even with the average
figure of 70 micron you could not get exact sharpness with a 1.4 lens as
it exceeds the focus depth.
Film flatness is mostly caused by the film cassette and the use of the
film. But the reported cases of sharpness plane differences might be
related to this phenomenon of film flatness.
More to come.
Heavy stuff, but I ama afraid you need it to know what is going on.
Erwin
Date: Tue, 16 Jan 2001
rmonagha@smu.edu (Robert Monaghan) wrote:
Most of the cos^4 fall off is due to the geometry of a rectilinear
lens. By introducing coma into the stop, as is done on lenses with
"tilting" entrance pupils, one cos term is eliminated resulting in
cos^3 fall off. Making the lens non-rectiliniar by introducing barrel
distortion can get rid of nearly all of the fall off at the expense of
geometric distortion.
None of this affects field curvature. If a lens is made to project
onto a curved field one term of the fall off can be eliminated but,
again, the lens will not be rectilinear.
---
Date: Tue, 16 Jan 2001
Robert,
Pinhole cameras with cylindrical film planes can reduce the light fall off
to a function of cos^2, with the drawback (i.e. artistic rendering) of
some curvilinear distortion. For a good discussion, see
http://www.pinhole.com/resources/articles/Young/index.html.
Bob
p.s. I am a great fan of your medium format site.
Robert Monaghan wrote:
Date: Wed, 17 Jan 2001
Pam Niedermayer pam_pine@cape.com wrote:
Well, you have two choices when building a panoramic
camera:
1. use a lens with very wide coverage; if you want this lens
to be rectilinear, then it will fall prey to the cos^4
fallof.
2. use a lens with narrow coverage and swing the lens. Note
that this avoids the cos^4 falloff, since you're using the
center of the field for the entire exposure. But now you
need to contrive to have the film be equidistant from the
lens nodal point; so you end up with a curved film plane.
So, yes, the reason for using a curved film plane is to get it
equidistant from the lens; but the reason for swinging the lens
is to avoid the need for a very wide coverage with the lens
(and in part, the cos^4 falloff that implies).
-Paul
Date: Wed, 17 Jan 2001
Not exactly what you're considering, but for enlargement of 5x7 negatives
I routinely use a curved film holder in the enlarger head and a curved (in
the other direction) paper holder. That combination corrects for
curvature of field in the enlarging lens. It also holds the negative more
securely. Even a good lens like the Componon I'm using has enough field
curvature to show at apertures as small as f/16 or so-- using flat
geometry. All of this has very little to do with the cosine loss, of
course, since the curvature is so small.
- Larry Whatley
From: ppestis@aol.com (Ppestis)
Thats what nobody ever really mentions !!
The Pentax pressure plate keeps the film flatter than any other medium
format camera. So what you may think you are getting in a more expensive
lens with other MF systems, you can lose with a film back that can't hold
the film flat. A good used Pentax body is so cheap you can buy another
body instead of a film back.
From Leica Mailing List;
hey george and LUG,
the vacuum back is indeed only available on the 70mm. the 220 backs
unfortunately don't have the vacuum system a la contax 645 (or rtsIII.)
the rollei is pretty sweet in 3 ways, though, in regard to film flatness.
1, the back's film plane is determined by the body, not the insert, like a
haselblad -- this is why it's important to get the matched set with a
hassy back. the back locks tight with 2 opposing buttons, the built-in
darkslide glides down and the film rollers and pressure plate push against
the camera back.
2, roll film is held to the pressure plate at 8 points, helping flatness,
especially in the corners. and 3) that the film path is pretty straight,
unlike the contax or hassy. easier to keep flat.
hope that clears up a thing or two.
kindest regards,
kenny
Date: Thu, 2 Aug 2001
http://www.rollei.de/en/produkte/mittel/magazindata70.html
It was on the site after all, at least in the 70mm flavor. I'll keep
digging for the 220, which, again, I'm pretty sure -- although not 100%
certain -- exists.
Date: Sun, 24 Jun 2001
: news.smu.edu rec.photo.equipment.medium-format:29922
Another cause for out of focus at the corners is film buckling. Did you
have the film pressure plate rotated to match the film (120 or 220). I
have also seen where the film pressure plate springs have come out and
there is insuffictient pressure to hold the film flat in the film guides.
Also, do the film roll pressure springs rub against the film so that the
film is kept snuggly wound? A loose roll pressure spring could allow the
film to buckle.
karl
"MRose" xtr5@Yahoo.com wrote
Date: Thu, 09 Aug 2001
I believe Minox briefly marketed a model where the film pressed against
the rear element of the lens. Optically this made some sense since, given
the tolerances in subminiature photography, the reputed additional
flatness gained by pressing against an optically flat glass surface would
aid resolution. But, they dropped it, because advancing the film in cold
weather caused static discharges that register on the film.
Regards,
....
Date: Thu, 09 Aug 2001
You are talking about the minox 2 - a very short lived model.
The reason it was canned was that dust got into the gap and scratched
the film. The only person I know who has one and shot with it says that
aside from the scratches it was an amazing lenses - high praise
considering how good the later Minox lenses are
j
Date: Fri, 03 Aug 2001
Can you ask at the shop where you will be buying from if they could let
you run a quick roll through each camera and then you could see for
yourself if there is a difference? I have the contax, but havn't tried the
Mamyia, but also didn't like the feel and size of the focusing ring on the
Mamyia, and didn't like the idea of having to switch a lever every time I
wanted to either manual focus or auto focus. I am sure that the mamyia
lens is going to be very good.
I have heard some negative comments about unsharpness with the mamiya
645AF in general. Zeiss made a study on film flatness amoung various MF
cameras stating ( you can find the article on their web site), amoung
other things that 220 film lies flater then 120 film and different cameras
do a better job of keep the fillm flat then others. The new reversable
back for the Rollei got the best marks ( I don't know if they compared the
vaccum insert for the contax), but what was most interesting is that they
made the comment that they now know what causes the unsharpness problems
with the Mamyia. One can only assume that they meant that the film holder
on the Mamyia is not of the best design although they didn't come out and
directly say that.
Of course, you could say that Zeiss is not going to be the most objective
source for this info as they are involved in the selling of competitive
products so take it for what it is worth.
mike
...
Date: Thu, 28 Jun 2001
"Ladagency" ladagency@aol.com wrote
William Garnett, who has taking aerial photos for over 50 years, says the
Pentax 6x7 has the flattest film plane of any camera (120 or above) he
knows of. That's why he uses a Pentax 6x7. Most 120 cameras with
removable backs are notorious for not having absolutely flat film planes
because they wind the film backwards from the natural curl of the film.
Remember that he often shoots at wide open apertures with minimal depth of
field.
Another interesting point that I have heard some people make is that a
Pentax 6x7 body costs about the same (or less) than a Hassy film back. I
don't know if he looks though the viewfinder or just aims the camera, but
I don't think the "SLR" part is the issue.
Date: 29 Jun 2001
Roland roland.rashleigh-berry@virgin.net wrote:
One can not determine accurate focus in a 35 mm or roll film
camera using a piece of ground glass. On axis, the focus
position is in front of the pressure plate at a distance equal
to the film thickness in 35 mm and 220, or the film plus paper
thickness in 120. In order to set focus accurately you need
to place a piece of clear glass or plexi in the pressure plate
position (not on the film rails), and add a section of developed
film or film/paper cut on an angle to form a "knife edge" for
focusing. The technique is used routinely for astrophotography.
If you want a detailed description, search google for my old
posts with the term "knife edge".
From: artkramr@aol.com (ArtKramr)
Newsgroups: rec.photo.equipment.35mm
Date: 02 Mar 2002
Subject: Re: NEW LEICA M7. The verdict.
>Maybe in another 45 years, they might actually do something about
>that film loading mechanism... but then again, who knows, it might
>be a Leica cult thing.
No. It is a loading system that positions the film flatter in the film plane an
contributes to Leicas superior image quality.
Arthur Kramer
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer
From: Franck Maubuisson fmaubuis@club-internet.fr
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Fri, 15 Feb 2002
Well, a wide angle gives a lot of D.O.F. but a small difference in the distance
between the lens and the film results in a big difference in focus and you can
observe this: if you turn the focusing ring of a wide angle from infinity to,
let's say, 2 meters, the lens doesn't move very much. I once had an
ill-calibrated P60, I got decent pics with the 80 and 180 mm, but it was
difficult with the Flektogon.
Stephe a écrit :
> Franck Maubuisson wrote:
>
> > I think this is right, but this should be enough to be annoying with the
> > 50mm Flektogon. My experience with kievs is that the slightest
> > miscalibration of the focusing screen results in out of focus shots with
> > this short lens. Maybe they corrected the focusing screen calibration for
> > use with the glass ? Optically, this should work.
From: "eMeL" badbatz99@hotmail.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Sun, 17 Feb 2002
Q.G. de Bakker qnu@worldonline.nl wrote
> ...
> But i am afraid when making my response i concentrated too
> much on the point that depth of focus indeed is small, less so
> on the point made by eMel that stopping down is ineffective. Sorry!
First of all, if you quote me (or anyone...) do it either accurately or not
at all.
Here is what really I wrote about it:
" ...and even slight problems with film flatness (or a lens
mount/registration distance) show up us unsharp areas on the negative
*practically regardless* of the f/stop used."
Here is a what the depth of plane of focus may look like at different
f/stops.
f/1 .003172 mm
f/1.4 .006216 mm
f/2 .012688 mm
f/2.8 .024864 mm
f/4 .050752 mm
f/5.6 .099467 mm
f/8 .203008 mm
f/11 .383812 mm
f/16 .812032 mm
As you can see, at f/2.8 (the value of f/stop which started our
conversation) the depth of the plane of focus is a puny (measly,
whatever...) 0.0248 mm - 0.000978 inch... With a well-adjusted camera
(aligned lens mount, 100% proper lens registration distance, fully
collimated lens, 100% straight film plane, straight magazine /camera back
mount, fully aligned film pressure plate and *no film curl*) that's enough,
but throw in some practical tolerances and you may be easily off on parts of
the negative, even at f/16...
Moreover, research shows that in some cameras - despite being 100%
adjusted - one should finish a roll within 1 hour or so or risk having
geometric changes to the film plane (various forms of film curl...)
Now... is stepping down "ineffective" or merely "practically
insignificant..?" You tell me...
(I postulate that it it's effectiveness is practically insignificant...)
Good shooting!
Michael
From: "Q.G. de Bakker" qnu@worldonline.nl
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Mon, 18 Feb 2002
Stephe wrote:
> Interesting, thanx and like I said I couldn't imagine it makes no
> difference. It seems odd that a longer lens would have more depth of focus
> but weirder things have happened :-)
It's no mystery. Only geometrics.
A longer lens (in general) is further away from the film plane. The angle
subtended by the beam passing through the lens's exit pupil to be focussed
on film will decrease with increasing distance. This means the circle of
confusion will grow at a lesser rate when the film plane is moved, hence the
distance through which the film may be moved before the image becomes
noticeably unsharp (= depth of focus) increases.
So depth of focus is directly proportional to the acceptable diameter of the
circle of confusion, the f-number of the lens, and focal length. Depth of
focus also changes with magnification, but in general photography
magnification is small enough to be negelected.
From: "David J. Littleboy" davidjl@gol.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Mon, 18 Feb 2002
"Q.G. de Bakker" qnu@worldonline.nl wrote:
>
> It's no mystery. Only geometrics.
> A longer lens (in general) is further away from the film plane. The angle
> subtended by the beam passing through the lens's exit pupil to be focussed
> on film will decrease with increasing distance.
Uh, I drew a few triangles and managed to persuade myself that the angle of
the cone of rays focused to a point depends on the f-stop, regardless of
focal length.
The envelope of the cone for a 100mm f/2.0 lens is an triangle with a height
100mm and a base 50mm, but that for a 200mm f/2.0 is a height 200mm and a
base 100 mm. As seen from the film plane, those incoming cones have the same
angle, and the same DOfocus.
> This means the circle of
> confusion will grow at a lesser rate when the film plane is moved, hence the
> distance through which the film may be moved before the image becomes
> noticeably unsharp (= depth of focus) increases.
Only if you compare lenses with identical aperture diameters (not
f-stops)...
> So depth of focus is directly proportional to the acceptable diameter of the
> circle of confusion, the f-number of the lens, and focal length.
I think the f-number ends up (effectively) incorporating the focal length,
so DOF is independent of focal length.
David J. Littleboy
From: "Q.G. de Bakker" qnu@worldonline.nl
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Mon, 18 Feb 2002
....
Let AB (=d, the diameter of the pupil/lens) be the base of triangle ABY the
top (Y) of which is the in focus point on film;
C the middle of AB;
v (lens to film distance) = MY;
DE the base of another triangle DEY, in which DE is equal to c, the maximum
acceptable size of the CoC;
and M the middle of DE;
MY will then be half the depth of focus.
Triangles ABY and DEY are similar, so
MY/CY = DE/AB
which leads to: MY = (DE * CY)/AB = cv/d
Depth of focus extends on both sides of the film, so DoFc = 2cv/d
Since f/d = N (the f-number), this can be rewritten as:
DoFc = (2cNv)/f
c = the maximum acceptable size of the circle of confusion
N = focal length/diameter exit pupil (= f-number (!))
v = lens to film distance (depending on the focal lens of the lens used, so
focal lengths appears once more)
f = focal length.
v/f = 1 + magnification (m), so the formula can be rewritten as
DoFc = 2cN(1 + m)
When magnification is small, 1 + m will not differe significantly from 1, so
the simplified form is
DoFc = 2cN
Next if we substitute a value for c = f/1000, and also f/d for N
the final form is
DoFc = 2fN / 1000
So depth of focus is directly proportional to both focal length and f-number
(f/d = N).
From: "eMeL" badbatz99@hotmail.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Sun, 17 Feb 2002
Q.G. de Bakker qnu@worldonline.nl wrote
> Depth of focus (roughly) doubles (!!!) when either f-number or focal length
> doubles.
> Using a 100 mm lens, f/4, and accepting f/1000 as the maximum acceptable
> size for the CoC, depth of focus is 0.8 mm. Not quite miniscule, is it?
;-)
Right... 0.8 mm (0.0315 inch) *is* miniscule. even with your rather large
value of COC.
As for your calculated value itself - photographic equipment in general
(and Soviet/Russian/Ukrainian in particular...) is designed, manufactured,
assembled and adjusted to certain tolerances. Think of the 0.1 mm
tolerances of the lens mount alignment, plus 0.1 mm tolerances of the lens
registration distance, 0.2 -0.4 mm of film back mount, 0.1 mm misalignment
of the pressure plate, and add film flatness issues due to curling,
humidity, etc. And - with the worst case scenario, which can be a normal
case scenario for Kiev - you can easily exceed the rather puny 0.8 mm...
Michael
From: "eMeL" badbatz99@hotmail.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Mon, 18 Feb 2002
Stephe ms_stephe@excite.com wrote
> Interesting that a K-60 has less problems/issues with film curl than a blad
> does.. Once the focus screen to film plane alignment is checked (mine was
> fine) film flatness is all that's left. While a focus screen out of
> adjustment is an easy fix, film curl caused from the path the film has to
> take through the camera, can't ever be repaired.
Yep. I did state on many occasions that IMO a properly adjusted 60 (6s) has
a very flat film plane. It has/may have a lot of other warts which will/may
make the final image not as sharp as that from - say - a properly adjusted
Hasselblad - but the film plane *alone* should be flat. Not so in the
Salyut/Kiev 8x models with interchangeable backs: film flatness issues in
these cameras are typically *much* worse than in a Hassy or even Holga :-)
Michael
From: hkrafft@polbox.com (Hartmut Krafft)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: film flatness
Date: 18 Feb 2002
Stephe ms_stephe@excite.com wrote:
> emel posted the following..
>
> ???
> DOF (in front of the lens) and Plane Of Focus (on film) are two different
> things, and no DOF can ever correct film flatness issues of cameras...
> "DOF" (in quotes...) on the film plane is miniscule and even slight problems
> with film flatness (or a lens mount/registration distance) show up us
> unsharp areas on the negative *practically regardless* of the f/stop used.
> Optics 101...
>
> Michael
> I've read several people saying that at small f-stops, slight film flatness
> issues aren't a big problem anymore yet emel is claiming that no amount of
> stopping a lens down will affect/correct this. This doesn't make sense to
> me. And if this IS true, why would anyone use ANY camera that has ANY film
> flatnes issues like blads and other cameras of that type do?
There is a minuscule 'sharpness depth' around the film plane. How
deep it is depends on the criteria you're imposing: any object
that's not exactly in focus will not produce a sharp point on the
film, but a circle. Now, this circle may be so small that it may
resemble a point, when you look at it. So, 'sharpness' is a
question of the enlargement needed and your quality requirements
(or perfectionism ;-).
Usually, a 'rule of thumb' is set to determine what's still sharp
and what's not. You might say, for instance, that the circles
resulting from objects not excatly in focus may not be wider than
1/1000 of the focal width of the lens. (But, of course, you might
enlarge or reduce this margin according to your criteria, see
above...)
If you use this 1/1000 of focal width margin, you can work out a
ballpark formula for objects that are reasonably far away from
your lens (10-20 times focal width or more) to find out which
distance from the ideal film plane an object's image may have to
produce circles that are still below that margin:
d=(f*k)/1000
where d is the distance from the focal plane, f is the focal
width, k is the lens stop number (e.g. 2.8 or 5.6), and the 1000
comes from the above 1/1000 (arbitrary) quality margin.
So, with an 80mm lens stopped down to f/8, the distance from the
focal plan might be up to 0.64 mm, stopped down to 2.8, 0.224 mm.
Then, the maximum film bulge must not exceed this distance (in my
experience, at least the Kiev88 magazines easily show more
bulging...;-)
When you increase the quality margins, it's easy to see how the
depth of sharpness around the film plane decreases accordingly.
In fact, even the 1951 book I stole the above formula from
(Dr.-Ing. Helmut Naumann: Das Auge meiner Kamera, Halle(Saale):
Wilhelm Knapp 1951(1937), p.26 sq.) recommends to calculate DOF
on the grounds of 1/2000 f for 80mm, 1/3000 f for 100mm, and
1/4000 f for 150mm lenses (op.cit., p.32).
HTH
Hartmut
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 08 Feb 2002
Subject: Re: Kiev models - Film Flatness
Many years ago there was a Pentacon 6 club in the USA.
In their newsletter they advocated putting an optical flat glass
plate in the film plane and that solved the film flatness problem.
I would like to have someone do that adaptation on one of my cameras.
- Sam Sherman
From: Marv Soloff msoloff@worldnet.att.net
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Sat, 09 Feb 2002
... (quote above post)
Sam you may not need optically flat glass for this - try to find an old
glass slide (2 x 3 or 3 x 4), clean it down to the bare glass, cut to
fit, and glue it (use double sided tape) to the pressure plate.
Should work.
Regards,
Marv
From Hasselblad Mailing List:
Date: Fri, 08 Mar 2002
From: Peter Rosenthal petroffski@mac.com
Subject: Re: [HUG] A-12 backs
Not to worry at all about mismatched magazines! It's the case itself that
determines the film plane. The spring-loaded pressure plate on the magazine
only pushes the film against the rails in the case thereby (sorry for using
the word "thereby", I promise not to do it again) determining focus.
Perfect film flatness is very elusive, so lets hear three cheers for depth
of field!!!
Peter
--
Peter Rosenthal
PR Camera Repair
111 E. Aspen #1
Flagstaff, AZ 86001
928 779-5263
From: artkramr@aol.com (ArtKramr)
Newsgroups: rec.photo.equipment.35mm
Date: 09 Mar 2002
Subject: Why M Leicas load they way they do.
Leica's rigid back and pressure plate attached to a precision placed flap gives
more accurate film positioning in the focal plane and sharper images. It is a
variation on the "locked plate" design of 35mm professional motion picture
cameras (MItchell) and is simply a better, if costlier way to design a camera
back. If Leitz ever gives in to the damand for sloppy door loading as they have
in their SLR's, it will be the beginning of the end. But I am sure that they
will never compromise this critical design feature.
Arthur Kramer
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer
Date: Sun, 10 Mar 2002
From: Colyn colyng@swbell.net
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Why M Leicas load they way they do.
artkramr@aol.com (ArtKramr) wrote:
>>here are many others that perform as well which shoots down your
>>belief that the "flap back" doors are inferiour..
>
>What you need is a session with Leica engineers. Suggest that they "improve"
>Leicas with a flap back and see what they respond.
I have visited the Wetzlar factory (now Solms) a couple of times and
have talked to several engineers. If this door was so inferiour, they
would not have used it..
What I am saying if you would listen is the "flap back" doors are in
no way inferiour. Otherwise they would have been modified long ago..
They hold the film as flat as the Leicas..
I have used Leicas for over 40 years and they are still my favorites
but I also use other brands and have as yet found no problems or
degradation of the image because they use "flap back" doors..
Colyn Goodson
colyng@swbell.net
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 19 Feb 2002
Subject: Re: Kiev models - Film Flatness
From: Marv Soloff msoloff@worldnet.att.net
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Mon, 11 Feb 2002
Lassi Hippeläinen wrote:
>
> Marv Soloff wrote:
>
> > I do know that a number of super-accurate motion picture cameras used
> > the glass-film-pressure plate system to produce totally flat negatives -
> > i.e for aerial work and animation. Of course these cameras were
> > specifically designed to work with glass at the film plane.
>
> There also was a Minox model that had the rearmost lens touching the
> film. Becomes a problem with coated glass :-(
>
> > As far as adjusting springs to adjust tension, perhaps. Some film
> > holders cannot be adusted and can only be shimmed. Film flatness is an
> > interesting problem and seemingly a modern problem brought on by
> > advanced technology. Our working photojournalist forebearers did not
> > have this problem.
>
> The inventor in me starts thinking...
>
> In the olden times they used glass plates in stead of rolls. Suppose you
> attach a film sheet to a rigid plate with some sticky glue? You could
> even use photographic paper in stead of film. After developing the
> paper, feed it to a flatbed scanner in stead of an enlarger. A nice way
> to use all those papers that are useless, after demolishing the darkroom
> to make room for a computer :-)
>
> -- Lassi
Glass plates (emulsions on glass) are still used for many industrial
processes and for astronomy where flatness is super-critical. In a
properly adjusted camera using glass plates there is *no*
flatness/sharpness problem. So perhaps our forebearers knew something we
don't.
Regards,
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 12 Feb 2002
Subject: Re: Kiev models - Film Flatness
As a user of many different types of 120 cameras in over 30 years,
I am well aware of film flatness problems.
When you have focused properly, have the camera on a tripod
at 1/250th second and ruled out many other issues - and still get some
photos not critically sharp - you learn that film flatness is a
problem in medium format.
An top executive of a major camera company told me-
"film flatness problems are the best kept secret in the
photographic industry."
- Sam Sherman
From: "Q.G. de Bakker" qnu@worldonline.nl
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Mon, 11 Feb 2002
Marv Soloff wrote:
> Of course these cameras were
> specifically designed to work with glass at the film plane.
That's it. There must be some adjustment to compensate for the additional
glass plate in the optical path to keep infinity focus.
You can lengthen the camera's body length to do that, but (if i remember
correct) the change in optical path length also depends on the angle
subtended by the incoming rays, so different compensation may be needed for
different focal length lenses.
> As far as adjusting springs to adjust tension, perhaps. Some film
> holders cannot be adusted and can only be shimmed. Film flatness is an
> interesting problem and seemingly a modern problem brought on by
> advanced technology. Our working photojournalist forebearers did not
> have this problem.
The problem with pressure plates is that they only put pressure along the
edges of the film, leaving the biggest part free to bulg. Increasing the
amount of pressure will not help very much. Nor will increasing the film's
tension. The best way to keep film flat is by making sure it is forced
against the pressure plate over all it's surface. The way to do that is to
use a vacuum system.
From: "Q.G. de Bakker" qnu@worldonline.nl
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Mon, 11 Feb 2002
Lassi Hippeläinen wrote:
> > That's it. There must be some adjustment to compensate for the
additional
> > glass plate in the optical path to keep infinity focus.
> > You can lengthen the camera's body length to do that, <...>
> ^^^^^^^^
>
> Ahem, *shorten*, glass is thicker than air :-)
Indeed. That's why inserting a glass plate will lengthen (!!!) the optical
path. The camera thus should be lengthended also to compensate.
From: "Q.G. de Bakker" qnu@worldonline.nl
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: optical glass flat plate was Re: Kiev models - Film Flatness
Date: Mon, 11 Feb 2002
Robert Monaghan wrote:
> however, each time this thread comes up, I learn about more cameras that
> use this trick (e.g., Marv's movie camera examples) ;-) hassy lunar
> cameras, aerial cameras, and on and on. I am beginning to be surprised
> that more cameras didn't use them, rather than going the vacuum method ;-)
The reseau plate on Hasselblad lunar cameras (and photogrammetric cameras)
is not meant to keep the film flat, but to provide reference points (the
crosses) on the film, enabling precise measurements. Film's dimensional
stability isn't that great, so processing will introduce a distortion large
enough to (severely) limit photogrammetry.
From: Marv Soloff msoloff@worldnet.att.net
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: optical glass flat plate was Re: Kiev models - Film Flatness
Date: Mon, 11 Feb 2002
Robert Monaghan wrote:
>
> yes, I think it would be an interesting project, once you had a source for
> the optical glass of the right thickness and type, it would be a useful
> project for people to be able to replicate (like flocking an older Kiev;-)
>
> I have run into some of the glitches you mentioned in my experiments, but
> I am convinced that this is the solution to a really cheap and compact
> decent panoramic 6x12cm using older folders and stereo cameras, as I
> noted. The potential for a film bulge is much higher in an older folder
> with 6x12cm+ channel lengths ;-) But machining a really flat film channel
> and takeup mechanics is more complex than most of us want! see related
> notes at http://people.smu.edu/rmonagha/mf/postcard.html
>
> however, each time this thread comes up, I learn about more cameras that
> use this trick (e.g., Marv's movie camera examples) ;-) hassy lunar
> cameras, aerial cameras, and on and on. I am beginning to be surprised
> that more cameras didn't use them, rather than going the vacuum method ;-)
...
There may be a middle way for your 6 x 12 panorama shots:
Try to adapt a film holder to take both the film sheet and a suitable
piece of glass. You may want to strip an old front surface mirror of
both the backing and the silver to yield a "backing flat". Now comes the
tricky part - glue the unexposed film to the glass plate - my thoughts
here are to use an artist's sprayable frisket adhesive - and weight down
the sandwich so that the film lies perfectly flat onto the glass.
Using the adapted holder, make your exposure normally - the film should
be in the film plane with the glass behind it for support. In the
darkroom, strip the film from the glass, prewet to dissolve the frisket,
and process normally.
The other (more expensive) option is to query Kodak and the other film
houses to see what is currently available in a glass based emulsion and
adapt a holder to take the glass plate.
In any event, it would be interesting to see just how far you can push
the glass concept over 100 years after it was first used.
Regards,
Marv
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 12 Feb 2002
Subject: Re: Kiev models - Film Flatness
Testing the film plane on my Pentacon 6 with film in the camera and opening the
shutter to B and checking the film plane-
The film was slightly puffy on some frames and lying more flat on others.
And, while we would all like to perfect this and solve the problem I just
remembered that I rarely shoot flat artwork, flat subjects, but instead
people and other less flat subjects - so the film unflatness gets lost in the
curves of the subject and uses the depth of focus.
- Sam Sherman
From: Marv Soloff msoloff@worldnet.att.net
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: optical glass flat plate was Re: Kiev models - Film Flatness
Date: Tue, 12 Feb 2002
Robert Monaghan wrote:
>
> yes, though sheet film holders are often thought to be rather flatter
> than many rollfilm backs, and such adapters are often used when maximum
> film flatness and resolution are needed (e.g., rolleiflex adapter etc.).
>
> you can buy various glass plate emulsions and use them directly, assuming
> you can get repeatable dimensional positioning when putting in the plates
> (stresses etc.?). As you noted, this is cumbersome (darkroom changing bag
> etc.) in practice. But all of these solutions give up the very
> convenience of rollfilm use that draws most of us to MF over LF sheet
> film cameras...
>
> To me, the big attraction remains that all the problems of bulging film in
> long panoramic camera film channels (esp on older cheapy postcard folders
> or stereo cameras) might be cured with the right setup. Grant that you
> have to worry about dust, and polish glass edges so not scratching (easily
> done at any glass house), and the result may not be as ideal as a vacuum
> back or multi kilobuck flat back pan camera (fuji gx617?). But if a $20
> piece of 2 1/2" x 5 1/4" glass with polished edges means you can get pan
> photos and blow them up 6X or 8X, then it may be enough for many users.
>
> The older polaroid backs for hasselblad also had a glass plate, not for
> flatness issues but to conduct the image some millimeters from the film
> plane down into the back so the polaroid film packs were at the focus
> point. Some of these backs were used with p/n films for enlargements too,
> and this trick was usable there too (though a few glitches with bright
> flarey light source spreading). Other cameras used fused optical fiber
> plates costing major $$ (35mm etc). The bottom line is that despite
> problems like dust, these setups can work surprisingly well for many uses
> and users.
>
> So like Sam, I'd like to see someone who scopes out a full solution and
> source for glass corrector plates, with polished edges, anti-newton rings,
> coated etc. for such projects.
>
> and the example published in Modern Photogr. that Sam and I have cited is
> the basis for our excitement, in that an unacceptable lens/camera
> performance was raised to very good to excellent simply by eliminating the
> film bulge problems and film flatness achieved via the glass plate. How
> many cameras could deliver excellent instead of poor results, if only such
> a plate were installed? Hmmm?
>
> grins bobm
>
> PS since the focus shift is based on 1/3rd-ish the glass thickness, it
> should be the same regardless of which lens is used, so a simple shift in
> lens mount position (on a folder) should adapt cameras with multiple
> lenses.
You may want to source optical flats (good from 1/4 to 1/10 wavelength)
at http://www.surplusshed.com. Prices are astoundingly good. You may
also want to search the large body of information on flatness coming
from the many astronomy newsgroups who are at the forefront of this
flatness problem. Cutting and edge polishing optical glass is well
within the capabilites of the amateur photographer and the costs are
almost negligible.
I suspect that modern film bases (substrates) are much thinner than the
old roll or sheet film bases. I have no concrete data but it opens the
door to some speculation that the old films were less prone to buckling
at the film plane. Thinner substrates would also resist complete
relaxation (uncurling) at the film plane. You are going to have to go to
your primary sources for information as to the material used in the
substrates, the substrate thickness (and uniformity), the dimensional
stability of the substrates and the coating (emulsion) thickness and
uniformity. This now becomes "rocket science" and I do not have the
technical information at hand. Also, I doubt if Kodak or Fuji will tell
you these things.
Just some thoughts.
Regards,
Marv
From Hasselblad Mailing List:
Date: Wed, 30 Jan 2002
From: Gary Todoroff datamaster@humboldt1.com
Subject: Re: [HUG] How many film magazines do you have?
From: Robert Monaghan
>... and a ground glass back (for 500c/ELM/SWC)
The NASA moon shots show the reseau plate cross marks from a *plain*
glass-backed magazine. Does anyone have one of those magazines? My 70mm
Agiflite aerial recon camera has the little crosses on the glass plate, one
in each corner, and seems to keep the film exceptionally flat for those nice
Zeiss T* lenses up front (150/2.8 Sonnar and 350/5.6 Tel-Tessar).
Gary Todoroff
From Rollei Mailing List:
Date: 16 Apr 2001
From: keller.schaefer@t-online.de
Subject: [Rollei] RE: Rollei TLR back for optically flat glass
Bob,
some dust accumulates on the inside of the glass but that is not
(practically) visible on the slide/negative/print (theoretically though, it
degrades image quality). Any dust directly on the film can be seen
afterwards, as it could without a glass. You could even argue that the glass
prevents dust settling on the film.
If some dirt (or parts of the tape or backing paper) would stick to the
glass this would ruin the entire film until you open the back and wipe
over the glass before loading the next film. I did not experience this
but it can happen.
Sven
>Date: Sun, 15 Apr 2001
>From: "Robert Meier" robertmeier@usjet.net
>Subject: Re: [Rollei] RE: Rollei TLR back for optically flat glass
>Sven,
>Do you have a problem with dust on the glass?
>Bob
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 07 Feb 2002
Subject: Kiev models - Film Flatness
I learned from a veteran camera technician how to check film flatness in
rollfilm slr cameras. Remove the lens - load the camera with test roll of film
- used for this purpose. Set the shutter to "B" and examine the film plane
through the front of the camera on each shot with the shutter open. Use a plastic
pen and probe the film surface to see if it exhibits any puffiness or "bulging"
up from the pressure plate or any wavy un-flat areas. After doing this for a while
one gets to recognize a flat film plane and unflat one.
Of course, this will vary from camera model to camera model,
type of film used and upgraded versions of older cameras.
Normally cameras exhibitng a very flat film plane are capable of
very sharp results with good lenses.
Here is what my tests have revealed on Kiev Cameras-
Kiev 88CM and Kiev 88 with new "NT" back - very flat film plane repeatedly so -
all frames on a roll of film and roll to roll.
Kiev 88CM and Kiev 88 - with old type Kiev back - very unreliable
from back to back and exposure to exposure on the same roll. Exhibits
puffiness on the film bulging forward and some wavy sections.
These older backs can be upgraded and flatness improved.
Kiev 60 (my 1988 model) - Some wavy areas on the first few frames-
some puffiness. Later added 3/8" wide flocking at the side edges of the film
aperture in back of camera. Generally much flatter film plane overall.
Kiev 6C (1985 model) - different film plane than in Kiev 60 as
it also takes 220 film. Added wide (about 1") flocking at film plane
and generally flat film plane on all exposures.
Kiev 60 types vs. Kiev 88 types on film flatness issues -
The interchangeable backs on the Kiev 88 types can experience
variances in specs and tightness to the camera bodies - which can cause focus
problems. The one-piece Kiev 60 types have no back variations to deal with and
should have better focus integrity.
The "NT" backs have a newer design than the old Kiev backs,
in which the pressure plate presses the film solidly against two thin rollers -
at the top and the bottom of the frame - of the back
frame aperture. This helps to stretch the film taut and give a flat
film plane - even though the curved path design of the NT back has been known
to cause unflat film in other cameras. The straight across film path of the
Kiev 60 types lacks the curved path of the Kiev 88 backs - and helps to deliver
flatter film in this way.
My experience shows me that while the above works in theory-
this varies from each individual camera - one to another and the
type of film used - thicker or thinner.
Make your own tests to determine what your camera can do.
From: Marv Soloff msoloff@worldnet.att.net
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness
Date: Sun, 10 Feb 2002
...
Just to throw a bit more *$%# into the game, deBakker says that:
"Generally (depending on the refractive index of the glass) the focal
plane is only shifted by 1/3rd of the plate's thickness."
I can't comment on this, I have not done my homework in optics.
I do know that a number of super-accurate motion picture cameras used
the glass-film-pressure plate system to produce totally flat negatives -
i.e for aerial work and animation. Of course these cameras were
specifically designed to work with glass at the film plane.
As far as adjusting springs to adjust tension, perhaps. Some film
holders cannot be adusted and can only be shimmed. Film flatness is an
interesting problem and seemingly a modern problem brought on by
advanced technology. Our working photojournalist forebearers did not
have this problem.
Regards,
Marv
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 10 Feb 2002
Subject: Re: optical glass flat plate was Re: Kiev models - Film Flatness
Bob,
It was that very Modern Photography article (I have it) that started all this
interest in the 1970s in putting glass plates in the Pentacon 6.
The US Pentacon club members experimented with this concept and improved on it
- dealing with - Newton's rings, scratching, dirt,
winding pressure, shifted plane of focus etc. And they came up with solutions
to all of these problems.
Which makes me think I would like to have somebody adapt a Pentacon 6 camera I
have for this purpose and follow the Pentacon Club suggestions.
- Sam Sherman
From: "Graphic" graphic99@mindspring.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Kiev models - Film Flatness (improved with Fuji spools)
Date: Wed, 13 Feb 2002
A cheap, easy fix for inadequate pressure caused by "slack" in the film gate
is to use Fuji 120-spools as the take-up spool when using any brand of film.
The Fuji spool has a "T" shaped bit of plastic in the slot which graps the
film and pulls it more tightly across the film plane. This can be
demonstrated by the fact that Kiev's (all????) have a spacing problem.
Comparing the spacing with the Fuji vs non-Fuji take-up spool shows that
spacing between frames increases with the use of the Fuji spools. The extra
spacing would appear to directly relate to greater film tension at the film
gate with an expected better film flatness.
Wayne Catalano
...
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 13 Feb 2002
Subject: Re: Kiev models - Film Flatness (improved with Fuji spools)
All Kievs (120) have a spacing problem?
Sheer Nonsense!!
I have - Kiev 60, Kiev 6C, Kiev 88, Salyut-C, Kiev 88CM and
NONE of these has a spacing problem.
As for the Fuji spools - they are good and have the advantage of a
place to catch the hole in Fuji film leaders - which is an improvement over the
film leader sometimes pulling out of the spool slot when loading.
As for film flatness - that is an issue based on camera design and
film type and which image is where on a roll of film. Fuji spools
will do little or nothing to change these film flatness problems.
- Sam Sherman
Date: Fri, 22 Feb 2002
From: Eric Goldstein egoldstein@usa.net
To: rollei@mejac.palo-alto.ca.us
Subject: Re: [Rollei] Rollei Users list digest V10 #175
Dan Kalish wrote:
> The manual recommends against advancing the film until you're ready to take
> a picture. Reason: its difficult to reset shutter speed to or from 1/500s
> once the shutter is cocked.
some say better film flatness and less tension on the shutter spring are two
additional reasons to follow this practice...
Eric Goldstein
from kiev88 camera mailing list:
Date: Sat, 19 Jan 2002
From: Kevin Kalsbeek krkk@earthlink.net
Subject: Re: Film Flatness- could the rollers accentuate
Hi Giuliano,
I am inclined to agree with you. I liked the heat shrink tubing idea from the
negative scratch prevention viewpoint.
As Sam Sherman has pointed out, the old style K-88 backs, which I like,
probably because I began with them many years ago, can be easily adjusted to
provide enough tension on the pressure plate to assure good film flatness.
It occurs to me that there might be a downside to the H.S. tubing on the
rollers, might be, that while the film is flat, it may no longer be sitting
in the correct position for the lens to focus the image on it correctly,
unless it is stopped down. Don't know.
I was able to get a couple of K-60 extension tube sets from Mike Fourman in
Atlanta Georgia for the same price- $17 per set. I like them!!
Best wishes,
Kevin
...
from kiev88 mailing list:
Date: Mon, 24 Dec 2001
From: flexaret@sprynet.com
Subject: Re: focus shift ???
Olivier,
If you are sure that the finder screen focus matches what is at the back at
the film plane -
then the problem is unflat film at the film plane.
If you are using the old style Kiev 88 back - the springs in the pressure
plate grow weak and the pressure plate
does not press forward enough, so the film is too far back.
In the NT backs the film plane is usually pretty flat.
However, in the NT backs check that the rollers at the film plane are
properly aligned in the
spring clips and that they turn properly.
Use an outdated or unimportant roll of unused film.
Remove the lens and set the shutter to "B" open the shutter for each
exposure and check from the front with a plastic pen to see if the film is
lying flat for each exposure and is at the film plane.
For insurance I would only shoot macro shots at f8 or smaller apertures.
Best,
Sam
From rollei mailing list:
Date: Thu, 04 Apr 2002
From: Richard Knoppow dickburk@ix.netcom.com
To: rollei@mejac.palo-alto.ca.us
Subject: Re: Re: Re: [Rollei] Planar Sharpness
you wrote:
>you wrote:
>
>>>I have an F w/f3.5 Planar, 5 element version @ 1965. It is usually quite
>>>sharp centrally at all apertures, but has to be stopped down to f11 to
>>>achieve edge to edge sharpness. The lens looks good as far as I can detect
>>>and has been examined by both Harry Fleenor and Marflex and pronounced fit.
>>Harry Fleenor examined it, said all was well. Krikor at Marflex said there
>was a spacing problem, purported to fix it, but the lens still performs the
>same. My only other clue is that the right edges of the negatives (left when
>in camera) seem fuzzy compared to the sharp edges of the other sides. That
>could mean the pressure plate isn't holding the film in proper alignment (or
>could mean nothing).
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>BTW, my search for a solution to this problem was how I found this list to
>begin with, and although I have benfitted much from its collective wisdom, my
>Planar is still sub-par. All I have left at this point is incurable
>optimism.
>
>Allen Zak
Not the pressure plate. The lens board is tilted. The F has adjustments
for parallelism on the four tubular rods which locate the lensboard.
Earlier cameras use shims. The lensboard can be out of alignment even if
the trim panel is even all around compared to the front of the camera body.
Its aligned with shims.
Checking parallelism requires a machinists gauge and a flat. The
reference surface is the edge of the lens cell. It can also be checked with
an autocollimator and flat mirror.
If there is noticable defocusing at one edge it indicates considerable
tilt.
Another possibility, although not very probable, is a tilted lens
element. Most lens cells are such that the components can't be tilted, at
least without chipping or cracking them. The chance of the lens having an
element or component which was edge ground off center or with the axis
tilted is very remote but could have a similar symtom.
If the camera was in the hands of Marflex or Fleenor not too long ago you
might find out if either checked the parallelism. Marflex at least should
have an autocollimator, I don't know if Harry has one, probably he does.
The nature of the film gate in the Rollei is such that the film is
straight unless the back plate has suffered severe and visible damage. The
film actually runs in a narrow channel between the outer set of rails and
the back plate. The clearance is changed with switching from 6x6 to 35mm.
----
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com
[Ed. note: thanks! to Alan for sharing these tips and notes on film - 120 vs. 220...]
Date: Thu, 24 May 2001
From: Alan Davenport w7apd@home.com
To: rmonagha@mail.smu.edu
Subject: Yashica 24 and 120 film
There's a common conception, that TLR's such as the 124G, with an adjustable
pressure plate, are moving the focal plane of the system to accommodate either
120 or 220 film, depending on the position chosen. This is wrong.
The film's emulsion is positioned by the nicely machined guide rails on either
side of the picture area. The guides are fixed, and so the position of the emulsion
is fixed. By a remarkable coincidence, this location coincides with the groundglass
in such a way that both lenses will be in perfect focus at the same time.
The reason for the adjustable pressure plate, is to adjust the pressure (!) against
the back of the film. This is to compensate for the different thickness of 120 film,
which also includes a paper backing, vs. 220 film which has no backing but only
paper leaders that tape to each end of the film. Presumably, changing the pressure
ensures that the film will remain flatter, between the guide rails.
Here's the reality: I own a Yashica 24, serial no. L5121415. I have owned this camera
since 1973. It has start marks for BOTH 120 and 220 film. I have run many rolls of both
120 and 220 film through it, and never had a focus problem (at least not caused by the
camera!) The Yashica-24 uses 120 film perfectly.
Alan Davenport
w7apd@home.com
From hasselblad mailing list:
Date: Wed, 1 Nov 2000
From: Roger contaxaholic@yahoo.com
Subject: Re: Question about real need of a vacuum back...
First off, lets put things in perspective. Perspective
with respect to film flatness with 'Blad and other MF
cameras and a comment or two about mf format to other
formats.
Secondly, I'm concerned that we aren't chasing rabbits
that are difficult to catch. Are we photographers or
are we inflating the importance of the whole film
flatness issue out of proportion, because isn't it
really a non-issue to the majority of people in the
audience who view the finished enlargments?
Now, not to ruin anyone's day, but supposedly, the
Rollei 600x film backs hold the film flatter than
Hasselblad, due to the clamping film guides or
something or other. This is according to someone I met
at a Chicago camera store with access to all the 'Blad
and Rollei stock they carried at that time, who was
deciding on 'Blad vs Rollei. He compared both the
'blad lenses against Rollei, and examined the chromes
under a 200x microscope. He said the two were so close
that the differences weren't worth talking about.
However, with respect to Rollei, Schneider had the
edge on the lenses he checked out. He also said the
construction of the Rollei film back positioned the
film plane more consistently than 'Blads did. He did
not like the Rollei electronics, and heard several
heated complaints from customers returning their
equipment. So, he liked Rollei but didn't feel he
could rely on it due to early models with quality
control problems. His favorite two cameras: 903SWC and
Contax T2. Oh, by the way, Rollei also has a 70mm
vacuum back, very expensive though.
On the other hand, do many 'Blad users complain about
fuzzy pictures because the film wasn't flat enough?
Perhaps anything perceived is more due to mismatching
film back mechanisms against another film back that it
wasn't mated to, thereby introducing differences in
where optimum film placement is with respect to the
lens? I still don't see or hear complaints about this.
Not that it doesn't happen, it's just that I haven't
seen them. 'Blad didn't get to be the most widely
distributed MF system in the world by having film
flatness problems, but most salesmen have cautioned me
to not mix and match components for 'Blad film backs.
Besides Rollei, in comparison to other MF cameras, it
doesn't matter much whether the picture was taken with
Rollei, 'Blad, Contax, Pentax, Bronica, Fuji or Mamiya
7 II. They all make the film flat enough. MTF curves
and lines/mm are all nice and well, but has anyone
ever made a demonstrative graphic example that shows
the difference between say, 67 lines/mm and 62
lines/mm? You have to blow the picture up so large
that it approaches ludicrousness. You have to
graphically attach the numbers with an actual picture
to grasp the significance, or lack thereof. I've seen
this done only once with Sinar literature, if memory
serves. Maybe someone knows of a web link that
graphically shows this sort of thing?
With respect to different formats, I think that the
smaller the format the less leeway you'll have for
errors in film flatness. If anyone really wants to be
'King Of The Hill', you should consider shooting large
format, like 8x10. I've got 8x10 velvia chromes that
leave no argument when compared with medium format.
Sure, medium format can capture more lines/mm, but so
what? Put an 8x10 chrome on a light table alongside a
MF and 35mm chrome of the same subject. Viewers won't
even see the MF. It's just no contest. Does anyone
question whether the 8x10 sheet film was held flat
enough against a sheet film back? Nope, never comes
up. Does anyone looking at the chromes care? Nope,
because the overall picture, composition, exposure,
colors, etc. all work together to create a visual
impact on the viewer. Film flatness just isn't that
big of an issue.
Your milage may vary, of course. 8-)
So, what's the point in bringing this up, you wonder?
The bottom line is that what we're talking about here
with MF film flatness, there just isn't going to be
enough difference for the average person to notice
unless the print is absolutely humongous, and even
then you'd probably have to point it out to him and he
wouldn't even care because he's so overwhelmed by the
colors, the size of the print, the composition, that
what you're talking about significantly dwindles in
importance by comparison.
--- Simon Lamb simon@sclamb.com wrote:
> Michael
>
> Film flatness is indeed an issue but I am sure it
> will not be one that
> bothers the majority of Hasselblad users. Take an
> image with a Hasselblad
> and either a 120 Makro Planar or 180 CF Sonnar and I
> do not think any of us
> would complain about softness, even wide open. If
> you decide to go the
> Hasselblad route you will not be disappointed.
>
> Simon
>
> Michael R. Hinkle wrote;
>
> > Let me start by saying hello to everyone on the
> list, as I am new. I look
> > forward to learning much from this group. I have
> been shooting 35mm
> > seriously for 4 years and am looking to move into
> medium format. I have
> > several friends that have recently moved to the
> Contax 645 system. They
> > profess the virtues of the vacuum back on the
> camera which in theory sucks
> > the film flat while the shutter is open. The
> Contax literature implies
> film
> > in medium format cameras has a tendency to bow or
> curl thus resulting in
> > slightly soft images when shooting with a lens
> wide open. Can anyone shed
> > some light on this for me. Let me state I am not
> trying to incite a
> series
> > of Contax flames, I am only looking to make an
> informed decision when I
> > purchase a medium format system.
> >
> > Thanks,
> > Michael
> > www.mrhphoto.com
From rollei mailing list:
Date: Mon, 04 Dec 2000
From: Michael Levy yvel@adelphia.net
Subject: [Rollei] Re: Curved film planes
Javier wondered if curved film planes might nit be a good thing to revive.
I have no idea, but from my recent attraction to Minoxes ( I have five now,
and am shooting for eight of them so I can make a Minox menorah for
Hannukah) and subsequent studies of Minoxiana it seems that the curved film
plane was a way with small. low-tensioned film strips, to correct for image
curvature from thelens. When Minox was bought/recued by Leica a new curved
lens with a new curved film plane was adopted and soon abandoned. This model
became the MOST troublesom-- could never really clean it properly due to the
tight clearances so folm was often scratched. The other earlier Minox
lenses were ok,aswas the Complan. But when the camera was redesigned for
electronic shutters the company adopted a flat lens and flat film plane -- I
suspect computer-aided design made this easier to do -- and preferable. The
drawback to the newer cameras, IMHO is twofold -- besides being battery
dependent the suckers don't have those neat low speeds below a 30th.
signed
'Tiny" Levy
From camera makers mailing list:
Date: Thu, 18 Oct 2001
From: Gene Johnson genej2@home.com
Subject: Re: [Cameramakers] Thin glass for a within-camera platen - thanks for help
Brian,
I had a long conversation with some folks lately about film flatness.
The problem gets worse as the format gets bigger, and if we're trying to
get the last l/mm out of things like the good people on this list
certainly are, then it's something worth paying attention to. Coated
glass would be a great idea, if you can find it, that would be a lot
more important than thinness in my opinion. By all means use the most
effective lens shade possible, and of course, the glass will have to be
perfectly spotless all the time. Everything, everything on the glass
will be on the negative. I like the vacuum idea for that reason. I'm
building a camera now that I would like to make a vac back for. I
haven't even started on that, I would love to hear any suggestions along
those lines myself. I had kind of wondered if something like a computer
cpu fan or two or three might be enough if it was done just right.
Gene
From camera makers mailing list:
From: "george jiri loun" george.jiri.loun@urbanet.ch
Subject: Re: [Cameramakers] Thin glass for a within-camera platen - thanks for help
Date: Thu, 18 Oct 2001
Hi Brian,
I dare to disagree with some of your points... The page about film flatness
you cite is very much an academic talk. Just look at the bottom of that
page to find out that most of the taking apertures, especially for the
medium format, are well enough in the tolerance of the depth of focus...
taking 0.2 mm as the buckling value of the film. Contax solution was much
more publicity for the new camera than a real advantage, most professional
photographers agreed about it. I have been taking pics for photo agencies
for more that 10 years and I never heard about one photographer who would be
taking better pictures than the rest of us because of the Contax ceramic
vacuum back. Or do you really belive that manufactures could not put a
glass back to their cameras if it were such a great advantage?? The reason
why they don't is simple - it brings more of disadvantages than the
"buckled" film in our cameras. The internal reflection is just one of
them... Contrarily to what you think the glass thickness doesn't change the
internal reflection.
I have made a camera with 6x24 roll film back inside, no glass of course,
and I can tell you than with a 8x loupe I find details on the slides that
are invisible to the eye when taking the picture! No recognisable unsharp
spots, except for wind in trees (300 mm Nikon lens). As you don't make 2 m
prints of that format, (and even if you did it would still be fully sharp as
seen through the loupe!) you can be very sure there is no problem with a
buckled film. Surely, you can invite an academician with a microscope and he
will write yet another web page about the topic but for the practical
purpose of photography you will not gain anything...
From camera makers mailing list:
From: "ZoneV" ZoneV@web.de
Subject: Re: [Cameramakers] Thin glass for a within-camera platen - thanks for help
Date: Fri, 19 Oct 2001
Hello,
I am a little late for the discussion.
Schott Germany sells Mirogard for high end picture frames.
It´s only in 2 and 3.2 mm thickness. But it it´s coated: Transmission 99%
Reflection 0.9%.
It cost about 240 DM per square meter. Thats about 120 Euro. Prices for 2mm
thickness and maximum formats 1.7 * 1.2 meters.
Sorry for my bad english :-(
Markus
From: dickburk@ix.netcom.com (Richard Knoppow)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Depth Micrometer Purchase?
Date: Sat, 25 May 2002
....
For reference the ISO-ANSI Standards for film plane placement in
sheet film cameras is:
Size Location Tolerance + or-
4x5 0.197 0.007
5x7 0.228 0.010
8x10 0.260 0.016
Dimensions in inches.
This is the distance from the reference surface for the film holder
to the film surface. It is the distance from the reference surface to
the ground glass.
For checking the film in a film holder it must have film in it.
Most sheet film is 0.007 inch thick.
---
Richard Knoppow
Los Angeles, CA, USA.
dickburk@ix.netcom.com
Date: Mon, 27 May 2002
From: "Greg" gregpam@ozemail.com.au
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Depth Micrometer Purchase?
Great subject. Never seen it up before , reckoned no one cared. Sinar
reckon on .3 mm that's about 12 thou. Richard quotes 7 thou. Truth is if
your limits are too high there would be nothing good enough to pass.
Some of my slides are ok, i.e. < .3 mm. Most are right on the border. I've
only ever taken one back for exchange and it was way out. The dealer was
quite fascinated by the testing demo. I feel he thought I was a bit nuts.
I use a motor cycle TDC dial gauge. It's small and comes with a fitting
enabling it to be screwed into the spark plug hole. I use a straight piece
of aluminium twice the width of the back.and the device is threaded into the
middle. First check the GG and make shure that it's flat to the back and
adjust (zero)the gauge. Then with a sacrificial film loaded one can check
to see if the film holder is parallel to the GG. and the same depth i.e.
from the lens, by sliding the alum. across the face of the film. I allow up
to .3mm
What ever you do don't check your Polaroid back. The shock might kill you.
And Polaroid just don't give a dam. Still its better being alive taking
blurred pictures that dead and not taking any. My new back was something
like 40 thou. out, yes one whole mm!! On inspection of other backs at the
shop including the rental ones I found mine to be the least out.?? One was
over 70 thou out of Parallel to the GG and about 20 thou. further from the
lens to boot. The Polaroid rep wondered what I was on about. Now if I was
to buy a digital thingamabob and join the screaming headlong rush to
consumerism my problem would cease to exist?
Was it Einstein that said problems can neither be created nor destroyed only
shifted from one less than perfect albeit satisfactory long term
photographic system to an extremely short term plasticised version.
--
-
-- Greg. -- gregpam@ozemail.com.au
From hasselblad mailing list:
Date: Tue, 28 May 2002
From: Alison Napier napier.images@virgin.net
Subject: [HUG] Accidental experiment with A12 back
In the past I've seen people ask about the problems involved in leaving a
roll of film in a Hasselblad back, so I thought I'd post my accidental
findings in case anyone's interested.
I inadvertently left a roll of Provia 100F in a spare A12 back that I
hadn't used for about 8 months. I was about to chuck it (as I didn't need it
anyway) or throw it in the fridge to develop myself when I get the time, but
curiosity got the better of me.
I shot the last few frames remaining and sent it off to the pro lab that I
normally use, fully expecting it to a) be very bent/curved across a couple
of frames and b) probably having lost a good deal of resolution or contrast
after leaving the film out of the fridge (and past its use-by date!).
Guess what? I shot the same subject on another roll of fresh film at the
same time, and the only way I can tell the films apart is because of the
different subject on the earlier frames of the old film.
The back was stored in a room that's probably no more than about 16 deg C
most of the time, so it wasn't subjected to excessive heat, but I'm still
amazed that I could get away with it and that the film is as flat as the
other one.
I'm no longer going to panic if I have to finish a shoot before finishing
the roll of film...
Alison Napier
napier.images@virgin.net
From hasselblad mailing list:
Date: Wed, 29 May 2002
From: ShadCat11@aol.com
To: hasselblad@kelvin.net
Subject: Re: RE: [HUG] Film Loading Question
In this case, I believe Austin has it right. When starting out with
Hasselblad (Jurassic era?) I was one of those who didn't get the word on the
magazine film clamp and loaded improperly for some time. My ignorance was
masked by low sharpness demands of my subject matter (portraits) and/or by
using the lens stopped well down most of the time. However, the first time I
tried a large group photo at f8, there was a slight but noticeable sharpness
loss from one edge of the negative to the other. Tests confirmed that wider
aperture photos of similar subjects exhibited this characteristic. The
camera was examined by two reputable Hasselblad techs and pronounced fit.
Neither suggested I might be loading film improperly. For a long time I was
mystified until, by a chance occurrence, I learned the correct way to load
film. The problem disappeared.
My guess is that for many purposes, clampless loading might provide
acceptable results, so there are not enough complaints to alert even Hassy
specialists that there could be an issue. But I rely on my own experience,
which is that loading under the clamp can make a difference.
Allen Zak
....
From: "Ralph W. Lambrecht" RalphLambrecht@t-online.de
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Depth of Focus - Help?
Date: Fri, 12 Jul 2002
Dear Rob
Similar to the zone of sharpness surrounding the focal plane, known as
depth of field, there is an equivalent zone of sharpness surrounding the
film plane, called the depth of focus. As the film image is a scaled
version of the subject in front of the camera, the depth of focus is a
scaled version of the depth of field. The front and rear limits of the
depth of focus can be calculated from the depth of field as:
df'=f^2/(dr-f) dr'=f^2/(df-f)
where f is the focal length and dr and df are the depth of field
behind and in front of the focal plane.
Depth of focus increases with the circle of confusion, focal length and
decreases with focusing distance and aperture, but it is at its minimum
when the lens is focused at infinity. The minimum total depth of focus
d is determined as follows:
d=2cN
where c is the circle of confusion and N is the aperture of the lens
in f/stops. This simplified formula only determines the total depth of
focus when the lens is focused at infinity, but by using it exclusively
for the following application, we are always on the safe side of image
focus.
Ralph W. Lambrecht
circles wrote:
> Can someone explain about Depth of Focus. I don't understand all the
> math behind lens geometry but something is puzzling me.
>
> I have just read that for compound lenses Gaussian optics
> rules/measures should be used for calculations.
> If so then what does the formula for depth of focus become?
>
> Also I have now read that actual aperture is the virtual "entrance
> pupil".
> Does this imply that if I were to draw triangles to graphically
> measure depth of focus, the triangle base would be the diameter of the
> entrance pupil and the height would be the distance from the virtual
> entrance pupil to the film plane?
>
> TIA
>
> Rob Champagne
From: Leonard Evens len@math.northwestern.edu
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Distance to film plane
Date: Wed, 10 Jul 2002
circles wrote:
> I have just gone through the process of setting my ground glass depth.
> This is how I did it.
> I used the method of photographing a 1 meter ruler which was placed in
> a position extending from the lens front directly away from the lens.
> It should be on a slight slope so that the lens can see the markings
> on the ruler and the focus point is approximately in the center of the
> viewfinder.
> For the test use the shortest focal length lens which you have
> available. This is best because the depth of focus at the film plane
> gets narrower as the focal length of the lens gets shorter. Therefore
> short focal length lenses will show up any error in GG position more
> than longer focal length lenses.
Your comment confused me because I thought the depth of focus was
essentially independent of focal length, at least for distant objects.
But I think I understand the point after some thought. Here is my
analysis, and I hope someone will correct me if I got something wrong.
The standard formula for depth of focus (according to Cox's
"Photographic Optics") is
c x N x v/f
where c is the permissible circle of confusion in the film plane, N is
the f-number, v is the film to lens distance, and f is the focal
length. (The formula is also easily derived using similar triangles.)
For distant objects v is approximately the same as f, so the depth of
focus becomes c x N and is independent of focal length. Of course,
the definition of "distant" is relative to focal length. If u is the
subject distance, then v = u x f/(u - f), so v/f = u/(u-f), and the
above formula for depth of focus becomes c x N x u/(u-f).
If u is set beforehand, then the smaller f is, the larger u - f is,
and hence the smaller the depth of focus, as you state. But it
shouldn't be a dramatic effect unless the subject distance u is small
relative to the focal length. That of course in itself would be an
argument for using a shorter focal length lens rather than a long focal
length lens.
I think that may really be the point. For a fixed subject distance,
the depth of focus is larger for a longer focal length lens, and
depending on the exact numbers perhaps significantly more. But in many
circumstances, the depth of focus is essentially independent of focal
length.
> Use the widest aperture of the lens to make the image(narrower depth
> of focus at filme plane again).
> Use the smallest possible lens extension to make the image because if
> you increase the lens extension you will also increase the depth of
> focus at the film plane and make any error in GG position less
> detectable.
You probably don't exactly mean that since the smallest possible lens
extension is when the subject is at infinity. At infinity v/f = 1, and
the depth of focus is c x N exactly.
> I used a 72mm lens (4x5 camera) and focused on the 32cm mark on the
> ruler. This gave approx 10cm of bellows extension.
> Make careful note of the range of depth of field on the ruler which is
> sharp on the GG using a correctly focussed loupe.
> Ensure that no shift of postion of camera or focus happens when you
> insert film holder/back.
> Make the image, develop and check neg with a loupe.
> If the focus point on the neg is closer than it was on the GG then the
> lens to film distance is greater than the lens GG distance which means
> you have to increase the depth of the GG a little and repeat the test.
> The reverse also applies. It might be wise to make several images at
> the same time to verify that you are not getting inconsistent film
> flatness problems although this is probably more necessary when using
> sheet film holders.
> With my test set up I was able to detect a GG positional error as
> small as .05mm which is .002ins
>
> I doubt very much whether using depth measurements using a micrometer
> will be as accurate as using this practical evaluation
> method(especially if you use a bosscreen like I do).
>
> Rob Champagne
>
>
>
--
Leonard Evens len@math.northwestern.edu
Dept. of Mathematics, Northwestern Univ., Evanston, IL 60208
From: circlesofconfusion@ukonline.co.uk (circles)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Distance to film plane
Date: 10 Jul 2002
For a better explanation of why depth of focus is more critical with
shorter focal length lenses do a search on the usenet archives for
"depth of focus".
There is a message there posted by Michael Gudzinowicz on 2000/06/13.
Rob Champagne
From bronica mailing list:
Date: Thu, 9 May 2002
From: Wayne Openlander wro@compuserve.com
Subject: back/insert problem solved... I hope
Hi Stephen,
Yes, I think we are making progress on understanding the film flatness
issue in the Bronica S2 system.
1) I also see that when a roll is run through the camera in a relatively
short time, say minutes between shots, the film stays flat, however, as you
observe, when the back sits for a while the film develops a kink at the
bigger roller. Then when the frame is advanced this kink moves to the top
of the frame in the back. I measure a ripple on the order of 0.25
millimeters or even worse when the next frame is completely advanced.
I can see that in critical situations this this could create a focus
problem. Rationalizing things, because the top of the holder is the bottom
of the picture the problem might be rarely noticed and might even improve
the apparent depth of field in landscape photography.
I promise to play around a little more and try one of the double roller
inserts over the weekend.
2) I also see that two of my backs have a sticky roller at one end of the
opening in the back. On the sticky rollers the blacking has been worn away
leaving a brass streak on the roller where the roller contacts the film.
The surface seems too smooth to scratch the emulsion but I can't find any
way to rationalize this unwanted feature.
I promise to play with this some more too and report back on Monday.
Thanks,
Wayne Openlander
.
From camera makers mailing list:
From: N1861@aol.com
Date: Thu, 22 Aug 2002
Subject: [Cameramakers] Re: Cameramakers digest, Vol 1 #456 - 9 msgs
Does using the reply function work on this list work? I guess I'll find out.
Regarding a vacuum back.
Years ago I worked with an Acti (sp?) process camera that worked as a
projection devise like a huge horizontal enlarger as well as a regular
process camera. It had a glass back with a rectangular groove ground into the
glass at the perimeter of the film and a vacuum connection to that groove to
hold the film flat. The glass was clear so a light source could project
through it, but I've often thought of trying something similar with ground
glass for a view camera.
How about a modified bicycle pump as a vacuum soourse in the field?
Hi, I'm new by the way. Toying with making a lightweight view camera for
field use.
Has anyone made a ground glass from acrylic or polycarbonate sheet, as a
lighter weight alternative to glass?
Jerry Henneman
Date: Sat, 17 Aug 2002
To: cameramakers@rosebud.opusis.com
From: Robert Mueller r.mueller@fz-juelich.de
Subject: Re: [Cameramakers] Thanks replies
I have inserted some comments below at the "################"
Bob
you wrote:
>OK on the non-glare framing glass not making useful ground glass - I think
>it's useless for framing too :O)
>
>I understand the concept of the spacing of the emulsion relative to the film
>holder 'pressure plate', but if someone know's a spec or tolerance, that
>would be nice.
I can look that up, of give you an old reference but if you have a holder
measuring will be faster! I will try to find that number in my handbook and
give you the source.
>I could always start with a measurement on the film holder -
>
>pressure plate-to-film holder face and see what happens.
>
>I guess I'll find out if it's the same for different format film holders.
>
>I echo Paul van der Hoof's interest in mega-size film holders. I know
>someone sells a 20 x 24 film holder for $400 (Wisner?), but that's outta my
>budget.
>
>Another goofy idea I have is wondering if there is a way to develop vacuum
>thru air flow, like a Venturi tube or something like that...either a funnel
>to catch breezes (this is getting a little far-fetched), or maybe a
>flywheel/impeller that could be cranked to develop air flow.
#################You can buy pumps running on a water stream out of a
faucet; chemists use them (saves ruining a nice mechanical pump). For
portable use, look at the pumps on automated blood pressure devices. The
ones I have run on batteries (probably not long!) and the devices are not
too expensive. You probably could do better with a cheap, battery operated
vacuum cleaner. You need little pressure difference for such a back. The
battery lifetime problem will be worse but you will be able to capture the
film better with the higher air flow. And you ought to be able to take a
fair number of photos before recharging if you do not run the blower longer
than necessary.
>Or a battery-operated fan in-line in a hose...hmmmm, I'll have to try that.
##################### Is this different than any large format
photo? There is a way out and that is the SLR. In 4x5 or 8x10 that will
be a sight!
>Problem then is how to use a ground glass where the vacuum film holder
>is...probably have to remove the vacuum film holder, insert GG, focus, swap
>GG for VFH again and see if the subject has fallen asleep or left the scene
>already. My VFH doesn't have an back that opens.
>
>Murray
From camera fix mailing list:
Date: Sat, 31 Aug 2002 18:37:30 -0000
From: "jonyquik"
Date: Fri, 25 Oct 2002
From: Manu Schnetzler marsu@earthling.net
To: hasselblad@kelvin.net
Subject: [HUG] Negative carriers
> Aren't all the Holga posts getting a....trifle out of hand..
It should be easy enough to filter out or simply delete the message
since "Holga" is in the subject line... :)
To get back on more Hasselblad oriented stuff (well someone might still
say it's OT since I'm talking enlargers...), I have a question. Do those
of you still doing wet darkroom work use a glassless or a glass negative
carrier?
The reason I am asking is that I'm in the middle of reading "Edge of
Darkness" by Barry Thornton (excellent) and a lot of stuff he writes
goes directly against what I've been doing for ages. Regarding carriers,
he says: "If you use a glassless negative carrier, you might just as
well buy the cheapest enlarging lens you can find."
The neg is not kept flat (I did his test of looking at the reflection of
a light in a neg kept in my glassless carrier and he's right, it's far
from flat) and "no lens at any price can bring this non-flat negative
into focus all over its surface simultaneously, no matter how much you
stop down."
And of course stopping down too much brings problems of its own.
Any thoughts/experience?
Manu
Date: Fri, 25 Oct 2002
From: "Ing. Ragnar Hansen AS" raghans@powertech.no
To: hasselblad@kelvin.net
Subject: Re: [HUG] Negative carriers
The best is to use tension carriers if you want to avoid glass. These stretch
the negative to keep it flat, but you normally only can use them on larger
enlargers or printers.
Ragnar Hansen
Date: Fri, 25 Oct 2002
From: Manu Schnetzler marsu@earthling.net
To: hasselblad@kelvin.net
Subject: Re: [HUG] Negative carriers
Eric wrote:
> small. With 6x6, I think it is pretty flat. Again, it depends. A
> long time ago, when I used to process film with Kodak fixer+hardner,
> my negs were flat as ironing boards. I don't use hardner any more so
> the negs are a bit more pliable.
>
> Are you testing with anything bigger than a 6x6 like a 6x7 or 6x9? A
> 6x6 square is pretty rigid I think.
I'm looking at 6x6. The test is really simple: put a neg in the carrier,
look at the reflection of a light (he suggests a fluorescent tube light
but frankly any light would do) on the shiny side of the negative. I
have a Saunders 670 and the 6x6 carrier is nice and holds the neg very
tight, but the test clearly shows that the neg is far from flat. My
feeling is that it's as flat as it can get given the size of the neg. In
addition, the heat of the enlarger would only make it worse.
A side question to anyone who knows the Saunders and the carriers: what
size is the "Universal Glass Masking Negative Carrier for 670 and 6700
Series Enlargers" and is it anti-Newton? I'm also looking at the
"Anti-Newton Top Glass for Universal Negative Carrier (for 670 and 6700
Series Enlargers)" which might be a better choice (way cheaper too).
manu
From minolta mailing list:
From: "Kent Gittings" kent@ism.com
To: Minolta@yahoogroups.com
Sent: Thursday, November 07, 2002
Subject: RE: [Minolta] curved focal plane
Main reason why a lot of lenses are a little softer on the corners is
because the focal plane created by the lens is not perfectly flat. Only an
issue wide open most of the time. Macro lenses, because the light from a
close object is not very parallel, are generally super corrected for flat
field because the effect would even be worse. As a result a good macro lens
used for normal shooting tends to be sharper at the edges wide open than a
similar none macro lens. At least that's my take looking at the optical
formulas of various lenses.
Kent Gittings
From: Leonard Evens len@math.northwestern.edu
Newsgroups: rec.photo.equipment.large-format,rec.photo.equipment.medium-format
Subject: What is depth of focus?
Date: Wed, 06 Nov 2002
For some thirty five years, I thought I understood the difference
between depth of field and depth of focus, but I recently checked some
definitions in textbooks and elsewhere, and while I'm sure I understand
the optics, I'm not sure I understand how those terms are used by most
photographers today.
Let me give my definitions, obtained originally by studying Cox's
Photographic Optics, which unfortunately is not as clear as it could be
on this topic as well as others.
When discussing depth of field, at least theoretically, one assumes that
the lens is focused exactly at some prescribed distance in subject
(object) space. That produces an exact image plane on the negative side
of the lens. One then asks which points in subject space, not
necessarily at the focused distance, will produce images in that image
plane which are acceptably sharp,according to prescribed standards. One
assumes the lens is focused exactly and the film is exactly where it
should be.
When discussing depth of focus, again theoretically, one fixes a
presumed exact image plane the same way, but one then asks how far off
the actual film surface may depart from that image plane so that images
in the actual film will still be acceptably sharp, according to
prescribed standards, but only for points in subject space at the exact
distance one is focused on.
In both cases, one assumes the principles of exact geometric optics
apply, so one ignores issues such as lens aberrations and diffraction.
Since there is a one to one correpondence between points in subject
space and the points where their images come to exact focus on the film
side of the lens, the two notions are very closely related. It may be
that some people use depth of field when discussing anything that
happens on the subject side of the lens and depth of focus when
discussing anything that happens on the film side. But because of the
exact correspondence, without further qualification, that would seem to
make the distinction meaningless.
Depth of field calculations assume implicitly no problems with film
flatness or focusing on some presumed subject distance.
Depth of focus calculations tell us how far the film surface can depart
from where it should be, either because it isn't flat or because there
is some focusing error involved, but only for points in the presumed
exact subject plane.
One can of course try to combine both notions in one, but the analysis
gets pretty complicated if you do, so usually people try to keep them
separate. Of course, they aren't independent since in the end you are
looking at where the film is or should be and where certain points come
to focus on the film side of the lens.
It should also be noted that there is one important functional
difference between the two notions. Usually one focuses with the lens
wide open. One can then judge the depth of focus at that aperture. For
distant objects, the formula for the tolerable distance from proper focus is
+/- N*c
where N is the f-number, and c is the diameter of the acceptable coc
in the film plane. At that point, you would worry about fuzziness either
in how well you focus or in how far off the film is from its presumed
position. On the other hand, when you start worrying about depth of
field, you use the taking aperture. Indeed the point of such
calculations usually is to determine what that aperture should be so the
desired depth of field is obtained. Mathematically, the issue is
further confused in that if one concentrates on where points come to
focus on the film side of the lens in relation to the exact image plane,
the same formula +/- N*c applies, but with the taking f-number N used
instead.
If your lens or focusing knob has a depth of field scale, you can see
the distinction right on the camera. The middle of the scale
corresponds to where you hope to place the film plane for exact focus,
but there will be a certain amount of fuzziness either because of
focusing error or because of film flatness issues. This will extend a
certain distance on either side of where you actually set it. There are
depth of field markings on either side of the center position (which by
the way are determined by a geared down version of the formula +/- N*c).
Those markings when compared to the lens distance scale will tell you in
principle which distances remain in focus at the specified apertures.
But again at both ends there will be a certain fuzziness because of
depth of focus issues.
Is the distinction I am making consistent with the usual way these terms
are used today? Any other comments?
--
Leonard Evens len@math.northwestern.edu
From: Leonard Evens len@math.northwestern.edu
Newsgroups: rec.photo.equipment.large-format,rec.photo.equipment.medium-format
Subject: Re: What is depth of focus?
Date: Wed, 06 Nov 2002
John Stafford wrote:
> Okay, but what's an aperture? And what about that knurlley thing on the
> lens that makes the pictures fuzzy? And what is infinity? What is beyond
> infinity?
Believe it or not, points beyond infinity in subject space are points in
back of the camera. Their images are in front of the lens. You can see
it by using the formula
1/x + 1/y = 1/f
where x is the distance from the lens plane measured to the object
point, and y is the distance from the lens plane to the image point.
Normally both x and y are positive, but you can take them to be negative
which means that the corresponding points are on the wrong sides of the
lens plane.
--
Leonard Evens len@math.northwestern.edu
But of course you weren't interested in the answer.
Date: Fri, 08 Nov 2002
From: Leonard Evens len@math.northwestern.edu
Newsgroups: rec.photo.equipment.large-format,rec.photo.equipment.medium-format
Subject: Re: What is depth of focus?
Dan Fromm wrote:
> Leonard Evens len@math.northwestern.edu wrote
>
>>This long discussion of what mathematics is or should be and so forth is
>>very interesting. I've spent a lot of time thinking about it and once
>>taught a freshman seminar on that topic.
>>
>>But right now I would like to get back to may original question. Is my
>>interpretation of the terms "depth of field" and "depth of focus"
>>consistent with the way people use them today?
>>
>>You can go back and look at my original post, but let me review it
>>briefly. In either case you assume the lens is focused on a specific
>>subject plane in front of the lens which yields an exact image plane in
>>back of the lens. When you discuss depth of field you are asking what
>>happens as you move away from the exactly focused subject plane. When
>>you are discussing depth of focus, you are asking what happens if the
>>actual film surface is different from the exact image plane, either
>>because of focusing error or lack of film flatness.
>
>
> Leonard, I've been following this thread with puzzlement and horror.
>
> I understand why people care about depth of field and try to control
> it when capturing images. We want to control how much of the image is
> acceptably sharp, we don't want telephone poles sprouting from
> peoples' heads.
>
> But our working assumption has to be that our gear, whatever it is, is
> close to specification. We expect the film plane to be where it
> should and the film to be fairly flat. In any case, we can't see or
> control where the film sits relative to the lens, so what's the point
> of even thinking about depth of focus? Yes, I have the concept vacuum
> back, but my cameras don't. Please help me understand why you think
> your question is worth asking.
My actual reason is a bit involved, and I probably shouldn't go into it
here. It really doesn't have that much to do with the usefulness of the
concept itself.
But I do think asking about depth of focus, in the sense I've defined it
here, is worth a little thought, though as you say maybe not that much.
I agree there isn't a lot you can do about the film not being just where
it is supposed to be, but you might find that there is a systematic
error that you can correct for in focusing. More important, I think
everyone is aware that it is very difficult to be consistent about
focusing. It is probably useful to have some idea of how far off you
may be. Fortunately, you focus initially with the lens wide open, and
you usually stop down considerably for the taking aperture. If you are
using medium format or 35 mm and a lens that has depth of field
markings, you can see on the lens barrel how much your focusing error
tends to eat up the depth of field range. You can do something similar
by putting a scale on the focusing knob of a view camera, and some
cameras come with one already provided. I put one on my Toho and I find
it helps me a lot, both in figuring what aperture I need for the depth
of field I want and in seeing how much fuzziness there is in my
focusing. I think I've discovered that I have a very slight tendency to
focus in front of where I intend, or perhaps some slight variation in
the construction of the camera leads to that. Those are all depth of
focus issues.
Depth of focus was dramatically brought to my attention recently when I
managed to load one sheet in a 4 x 5 holder on the wrong side of the
slot on one side of the holder. The image on that side was pretty
blurred, and I couldn't imagine why until I did some experiments loading
film in the light. I guess I was just lucky before that.
--
Leonard Evens len@math.northwestern.edu
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 07 Nov 2002
Subject: Tweaking Focus on Med Format
What amazes me is the number of medium format SLRs and TLRs
I have examined over the years where the finder screen focus is
"slightly off" in comparison to the film plane.
Some manufacturers and repair technicians use various forms of flexible media
(ie. mirror mylar) in the film plane to set this focus through instruments
projecting a pattern through the taking lens
and examining the reflection, based of their assumption that
film is not truly flat in the aperture/gate.
This is an approximation, as no two types of film, rolls of film or
exposures on the same roll of film can possibly display the same exact amount
of "unflatness", if there is any to speak of.
I have examined SLR cameras without the lens on, and shutter open, and test
roll in the camera and found many camera brands to have good film flatness,
which implies to me that a groundglass at the film plane is far better to set
the alignment with rather than some flexible media.
After expoxying a loupe to the shiny side of a piece of 6x6cm groundglass I use
this on the aperture rails to compare to the
finder focusing screen setting and then set this, if it is slightly off,
to match the focus on the image on the groundglass.
Since I have always gotten sharper photos on test films after this adjustment
is made, I thoroughly believe many cameras need this adjustment to get the
maximum sharpness out of their fine lenses, without needing to stop down to do
so.
- Sam Sherman
From: lawrencereiss@yahoo.com (Lawrence)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Tweaking Focus on Med Format
Date: 11 Nov 2002
Does there tend to be much variation in film plane distance between
backs? I use the Bronica Sq system, and am wondering about whether
other users have found much variation between backs/shells, and
whether there is any provision for adjustment of each shell.
Lawrence
From: rmonagha@smu.edu (Robert Monaghan)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Tweaking Focus on Med Format
Date: 11 Nov 2002
re: play in camera backs
it is a good question, and an interesting observation. Most cameras with
interchangeable backs use some sort of hook system (Bronica S2/EC, or
Hasselblad..) in which there is a tiny bit of play in some mounts. But
given 0.1mm is a huge impact on film resolution (for wide open fast
lenses) such a small bit of play could be another problem area...
in fact, tests of the Bronica C series (non-interchangeable back version
of S2 and S2A) suggest that this camera may give better results in part
because of the above factor (play in back positioning). The film plane
can be more exactly positioned. Bronica also made a series of changes in
their backs and inserts, which may be related to this point too.
bobm
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 16 Nov 2002
Subject: Re: Film-flatness question
There are many reasons in medium format for less than sharp photos
other than lens quality and focusing errors.
Check the alignment of the finder focusing screen vs. what the film is getting.
Many finder screens can be out of alignment.
Film flatness - some cameras/backs have problems- others not.
I have found Bronica S2A 12/24 backs with the improved "A" insert to deliver a
very flat film plane. Of course these cameras have a finder foam problem and
alignment of the focusing screen to resolve.
Kiev 88/88CM - the NT backs deliver a very flat film plane.
These same backs come in a special Hasselblad model (new) for about $100 and
are a great bargain for Hassy and easier to load than
Hassy backs.
Old Style Hasselblad and Kiev backs can also deliver a flat film plane if they
are properly aligned, and there are several adjustments possible.
- Sam Sherman
From: "Art Begun" beguna@mindspring.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Film-flatness question
Date: Fri, 15 Nov 2002
Kodak had major flatness problems with 126 format. Even earlier, if
you remember their old Brownie Starflash which used medium format, the
optical system was actually designed for curved film.
From: "Q.G. de Bakker" qnu@worldonline.nl
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: why no fast MF lenses?
Date: Sun, 17 Nov 2002
Robert Monaghan wrote:
> I doubt there are any useful stats on current users of cut film backs ;-)
> I tried a search on older MFD digest archives, but they are not working(?)
> but that's where I suspect I saw the thread on cut film holders I recall?
>
> [...]
>
> so at least for the purposes of my argument, the cut film holders are
> flatter in hassy, and film bulges ("curvature") can have major impacts
> as a source of "unsharpness", as I've suggested, which seems to be a
> problem for zeiss hence the vacuum backs and recommendation to use 220?...
Yes, sheet film will lie flatter than rollfilm, if the sheets aren't too
large.
As anyone knows who has ever tried enlarging 4x5", or larger, using a
glasless carrier. Imagine what an 4x5" sheet looks like when you draw the
dark slide. Remember when TPan was released? It was thinner than regular
sheet film, and as a result was not held very well in the normal sheet film
holders. With the camera pointed down a bit, it not only bulged like nothing
else, it fell out. ;-) With larger sheets, bulge is a problem too. Though
obviously not caused by curl.
Sinar make nice film holders: sticky. As good as vacuum backs, without the
hassle.
I have seen the Zeiss article too. And you know my thoughts about the
"coincidence" of Zeiss' report on 220 film's better flatness charateristics
appearing just as they were introducing the Zeiss/Contax vacuum back? ;-)
Was it a "problem" looking for a "solution", or a "solution" looking for a
"problem"? I strongly suspect (yes, i don't know either) the latter:
Contax/Kyocera has a long history of playing with ceramic vacuum backs. They
were building those long before the Contax 645 even was a twinkle in its
parents eyes; they had decided photographers needed vacuum backs long before
the 120 or 220 film choice even became relevant to Contax.
But what i wanted to hear from you was why you think/how you know that "many
of the users of hasselblad cut film holders used these with the SWC series".
From rangefinder mailing list:
Date: Mon, 18 Nov 2002 20:42:01 -0600
From: Jim Williams
From: jo_stoller@yahoo.com (Jo Stoller)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: when .1mm is big ;-) Re: Film-flatness question
Date: 27 Nov 2002
hemi4268@aol.com wrote:
> f-32 1028 microns or about 1 millimeter.
The unit name 'micron' was abolished in 1968. The correct name is now
micrometre (or micrometer). If you understand the metric system, you
can immediately understand the size of a micrometre whereas the size
of a micron is obscure.
http://www.bipm.fr/pdf/si-brochure.pdf
http://ts.nist.gov/ts/htdocs/200/202/metrsty3.htm
Date: Thu, 12 Dec 2002
From: christopher.m.perez@exgate.tek.com
To: hasselblad@kelvin.net
Subject: [HUG] 500CM floating focus?
This is a question for those who are truly neurotic about such things:
- I notice that a point of focus can shift subtly as much as three inches
from frame to frame. Why?
- I think I have isolated two sources for this.
1) Mirror 'float' - it's very subtle, but I can verify this by simply
focusing on the groundglass.
2) Film back 'alignment' - here too it's very subtle, but I see this
when focusing on a two dimensional subject and compare frame to frame
differences and it appears that the film itself is shifting 'fore and aft'
ever so slightly.
Comments? Feedback?
- Chris [ http://www.hevanet.com/cperez/ ]
Date: Thu, 12 Dec 2002
From: Jim Brick jbrick@elesys.net
To: hasselblad@kelvin.net, hasselblad@kelvin.net
Subject: Re: AW: [HUG] 500CM floating focus?
The only single thing in the "focus" path is the mirror. I believe you have
a mirror return problem, that is, your mirror settles in a slightly
different place each time it goes up, then down.
You can prove this easily by using a ground glass adapter in place of your
film back. Compare the focus on the GG back vs the GG viewfinder.
Jim
Date: Thu, 12 Dec 2002
From: Godfrey DiGiorgi ramarren@bayarea.net
Reply to: hasselblad@kelvin.net
To: hasselblad@kelvin.net
Subject: Re: AW: [HUG] 500CM floating focus?
I was informed by a repair tech that the Hasselblad mirror position
floats on a couple of small damping cushions and that over time they
become less resilient and shrink, which affects the frame to frame
mirror position. His recommendation was that these damping cushions
should be changed every 8-10 years, depending upon the environment in
which the camera is stored (dry conditions tend to make them shrink
faster, in his opinion). I don't know the truth of this, but it sounds
like a possibility.
The other thing is that it's unclear from Chris' post whether he is
examining negatives or focus on the groundglass. If negatives, and he's
working with the camera secured to a tripod mount, then it sounds like
he's got a pressure plate problem: the film plane is changing a little
bit from frame to frame. That might mean it's time for a back overhaul.
Godfrey
Date: Thu, 12 Dec 2002
From: "David S. Odess" hblad1@attbi.com
To: hasselblad@kelvin.net
Subject: Re: AW: [HUG] 500CM floating focus?
While it is true that the Hasselblad bodies do have a piece of dampening foam,
the foam has nothing to do with the position of the mirror. The mirror
position, when the body is cocked (or wound) is determined by a metal stop. This
stop can be adjusted to the proper position if the technician has the proper
tools.
The only piece of foam that the mirror comes in contact with is at the top of
the front plate. This piece of foam acts as a dampener when the mirror flips up
for an exposure.
David S. Odess
Factory trained Hasselblad technician
From camera fix mailing list:
Date: Thu, 26 Dec 2002
From: "vasilievich1953 vivanov@kcs.iks.ru
Subject: Re: focussing issues
Be very carefully in checking focus in such a way. Because neither the
film(inner)rails nor the the outer rails are not coinside exactly with
the manufacturer specified focal plane of a camera. The focal plane is
a plane which apparoximates the curved film surface on avarage.
For a Nikon camera manufacturer specified distances from the lens
flange are the following: 46.45mm(to the inner rails) and 46.67 +/-
0.02 mm (to the outer rails).But its "register" (the distance to the
focal plane) is 46.50mm. Any Nikon lens are adjusted to 46.50mm for
infinity but not for 46.45mm.
That is why to adjust focus it is necessary to know manufacturer
specified distances of the camera or a reliable values of film bulge,
also film thickness and space between the rails.
As you know in the upper and the lower areas of a "landscape" frame
the film is tightly pressed to the camera pressure plate.On the
contrary in the central area the film has a bulge from the
pressure plate directed to the lens flange.The bulge is about 0.04mm
for 35mm camera, it is bigger for a MF camera.
At home it is possible to examine the distance from the inner rails to
central area of the film surface by accurate shooting of inclined
ruler at angle of 45 degrees to the optical axis of a lens.Before the
shooting it is necessary to very accurate focus on the the inner rails
using a piece of fine ground glass and a 10x loupe(you should focus
many times and calculate the average position of focus).Then if you
know the space between the rails, film thikness you can calculate the
film bulge and determine the average film plane(focal plane) of your
camera.
Victor Ivanov
...
From: "Sherman" sherman-remove_this@dunnam.net
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Ansel Adams and medium format
Date: Mon, 16 Dec 2002
"Max Perl" max_perl@post11.tele.dk wrote...
> Are the Hartblei backs build the same way as a hassy A12 back?....same
> mechanical quality?.....film flatness ect.?.....or maybe improved
> performance?
> It sounds interresting......
>
> Max
The Hartblei backs will hold the film as flat as the Hassy A12 back. As for
mechanical quality I would say there is probably a difference between a back
that sells new for $150 or less and one that sells for 6 to 8 times as much
(but I don't believe there is a 6 to 8 times difference in quality). Plus
the Harblei won't have the little Hasselblad 'V'. ; ^ )
As for general design the Kiev/Hartblei back is an improvement over the
Hassy design. The insert is removed by lifting it straight up out of the
back rather than sliding it in. You won't catch the paper backing on the
edge of the holder and tear it.
Sherman
http://www.dunnamphoto.com
From: "Q.G. de Bakker" qnu@worldonline.nl
Newsgroups: rec.photo.equipment.medium-format,rec.photo.marketplace.medium-format
Subject: Re: medium format and shift lenses
Date: Fri, 17 Jan 2003
Stacey wrote:
> >But one thing you mention, film flatness, is far worse when using sheet film
> >than when using roll film.
>
> I don't find that to be true. It seems much less likely to
> buckle/buldge and given the film path most roll film backs have, you
> have to shoot the whole roll pretty quick to not have pretty severe
> problems. At least with sheet film the base is thick enough where it
> stays fairly flat.
You never used TechPan in 4x5" format? These things are so flexible there is
a very real risk of them even falling out of the film holder when that is
tilted down a bit. Other film has a thicker base, true, but still flexes a
lot. Roll film is better.
From: "David J. Littleboy" davidjl@gol.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: when .1mm is big ;-) Re: Film-flatness question
Date: Tue, 19 Nov 2002
"Robert Monaghan" rmonagha@smu.edu wrote:
> from Depth of Focus equations, for a COC of 0.05mm using 6x4.5cm image,
> yields at f/2.0 a DOFocus of .2mm, for ANY f/2.0 lens, regardless of focal
> length or where the lens is focused (they aren't in DOFocus equations,
> only COC, aperture, and magnification (at infinity or so, that's ignored).
I've not (at least I don't think I have) said anything that depends on the
DOFocus. I'm concerned with placement of the "plane" of maximum sharpness in
object space.
> again, ANY lens used at f/2.0 (with COC of 0.05mm and M=0) is effected,
> not some oddball ultrawide lens or whatever your calculations suggest ;-)
You're the one who suggested a lens with a DOField from 10 feet to infinity
at f/2.0: a given DOField, an f stop, and a film format (COC) is enough to
calculate a focal length, which I did.
> That is equivalent to a mis-focusing error of .125mm at that film bulge
> point. Whatever the Depth of Field is at the selected COC and subject
> distance, the image on the film bulge point will be beyond those limits
> (+/-.1mm), and so out of focus - even though the rest of the image is fine.
> so this problem effects every MF lens of f/2.0 or faster speed (using
> these COCs) used wide open - the hassy 100mm f/2, the norita 80mm f/2 etc.
This assumes that your subject is exactly at the distance you focused at.
And:
> again, these effects are visible by out of focus patches in a flat field subject
Stop right there. That's exactly the problem.
There aren't any flat field subjects, and even if there were, you couldn't
line up the camera with them.
So there aren't any subjects for which I can tell the difference. So as a
_photographer_, I still haven't seen any examples where film flatness
problems on the order of +/1 125 microns matters.
The one place it _does_ matter is infinity focus, where it limits what you
can do with hyperfocal focusing.
One place it _might_ matter is images just shy of infinity focus. E.g. sport
s photography.
Which is why I asked about accuracy/repeatability of focus. If the focus
error is on the order of the film bulge, then film bulge is not the limiting
issue.
(Then there's the question of whether the focussing system assumes perfectly
flat film or splits the difference intelligently, i.e. should one always
hyperfocal by 1/10 mm or so at infinity or not?)
Again, this gets back to the original claim that film flatness is the
_primary_ reason for the lack of fast lenses. Lack of DOF, weight, price,
and performance compromises seem far more important.
> You can also open up a film back and often see ripples of film bulges,
> which will show you how unflat many backs are in holding film. Those
> bulges, if more than .1mm, can cause problems with fast lenses wide open.
FWIW, the "bulge" in the Mamiya 645 back involves a _depression_ near the
leading edge, placing the bulge near the center of the frame. And it's
definately worse on the next frame after letting the camera sit for 8 hours.
> On 6x9cm backs, the bulges are 0.02" or 1/2mm, which is a problem for ANY
> lens as fast as f/4 on those backs, and the reason many users report
> problems using such backs, and why film flatness problems are obvious
> there even when slower lenses are used....
Yes, I'd expect the bulges to have dimensions larger that -0/+100 microns,
even on 645, and our assumptions about what DOField we have are quite wrong,
since I'm scanning at 4000 dpi an notice when things aren't sharp.
I wonder if film bulge is enough less of a problem on 645 that that had
something to do with Hassy moving to 645???
The reason I'm arguing here is that this question bears directly on the
problem of lens evaluation. We use the MTF charts to infer the performance
of our lenses under practical conditions, and if the MTF charts
underestimate lens performance due to film bulge (which won't be an issue if
I move the lens forward 1/10 mm at infinity focus), I may make an expensive
incorrect purchasing decision.
David J. Littleboy
Tokyo, Japan
From: "David J. Littleboy" davidjl@gol.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: when .1mm is big ;-) Re: Film-flatness question
Date: Tue, 19 Nov 2002
"Robert Monaghan" rmonagha@smu.edu wrote:
> from Depth of Focus equations, for a COC of 0.05mm using 6x4.5cm image,
> yields at f/2.0 a DOFocus of .2mm, for ANY f/2.0 lens, regardless of focal
> length or where the lens is focused (they aren't in DOFocus equations,
> only COC, aperture, and magnification (at infinity or so, that's ignored).
This answers the question: the DOFocus at infinity will become unable to
compensate for film flatness at some f stop for _any_ deviation from
flatness. So it's trivially true that film flatness limits lens speed for
landscape photography.
I still don't think it's meaningfully true (i.e. fast lenses are out of the
question for other reasons), but we'll have to agree to disagree on that.
David J. Littleboy
Tokyo, Japan
From: morongobill@excite.com (Bill Mcdonald)
Newsgroups: rec.photo.equipment.medium-format
Subject: Leaving film in Medium format camera for extended period of time
Date: Tue, 25 Feb 2003
I am thinking of going m/f particularly trying the Mamiya 645e.
In a book about medium format I own it says you shouldn't leave the
film in very long as it will "dent" for lack of a better word.I know
this is a newbie question,probably the dumbest ever, but I'm asking
it because I have been known to not finish a roll for weeks.
Right now my Olympus IS3 DLX has a half used roll inside,been there
for 2 weeks, don't know when I'll use it up.Of course with my E-10 I
don't have that problem.But then on the other hand I don't have the
huge negative(or file size to work with in my landscape photos, like
Medium format).
Also I've followed the Kiev threads with interest, the 88CM and the
19M look promising as well.
Thanks for any help,
Bill Mcdonald in Joshua Tree
From: "Sherman" sherman-remove_this@dunnam.net
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Leaving film in Medium format camera for extended period of time
Date: Tue, 25 Feb 2003
Bill,
The film issue is because the film is larger and therefore somewhat more
difficult to keep flat, and because in many MF cameras the film follows a
sort of odd path reversing direction twice (difficult to explain, totally
obvious once you see it). So in the sharply curved areas of the film path
the film can sort of "set" with a curve that might not completely flatten
out when that area of film is advanced to position for exposure. However I
have left film in my Kiev 88CM back for a couple weeks without noticeable
adverse effects, but I don't recommend it.
Note that the Kiev 19m is a 35mm camera, not a MF camera. It is compatible
with the non-autofocus Nikon lenses.
The Kiev 88CM is a nice camera for the price and I own and use one
regularly. However the Mamiya 645E is priced very similarly and has better
quality control. The difference really begins to show up when purchasing
additional lenses or backs/inserts.
Sherman
http://www.dunnamphoto.com
From: Leonard Evens len@math.northwestern.edu
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Leaving film in Medium format camera for extended period of time
Date: Tue, 25 Feb 2003
Bill Mcdonald wrote:
> I am thinking of going m/f particularly trying the Mamiya 645e.
>
> In a book about medium format I own it says you shouldn't leave the
> film in very long as it will "dent" for lack of a better word.I know
> this is a newbie question,probably the dumbest ever, but I'm asking
> it because I have been known to not finish a roll for weeks.
I've left film in medium format cameras or roll film holders for
extended periods of time without any obvious deleterious effects. But I
never advance to the next frame until I am ready to take the picture.
Some roll film holders do have fairly complicated routes to the film
plane. The Hasselblad magazines are supposedly notorious for that. In
such cases the film might be sitting in a crimped condition, and there
may be a problem. Of my medium format cameras and roll film holders,
only my Rolleiflex TLR even comes close to such a configuration, and I
haven't noticed any problems with it.
...
--
Leonard Evens len@math.northwestern.edu
[Ed. note: how about adjustably unflat lenses? - ;-) ]
From: scott@wsrphoto.com (Scott M. Knowles)
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Wide angle flat field lense?
Date: 28 May 2003
entropy@farviolet.com (Lawrence Foard) wrote
> Does such a beast exist? I'm looking for something which could get
> about a 12 foot area of a wall from about 13 feet away.
>
> Thanks
> Larry
Other than macro and copy lenses, which aren't wide angle lenses (50mm
to 200mm) but designed with flat focus planes, the only two lenses I
know of are Minolta's (MC and MD versions) 24mm f2.8 VFC and 35mm f2.8
Shift-CA lenses. These two had variable focus plane control (VFC) of
the outer groups to change the focus plane from convex through flat
field to concave. The effect is minor in the center and only
significant at outside the center and at small apertures, but handy at
times, especially with the shift lens.
--Scott--
From: photographyworks@yahoo.com (Bernard)
Newsgroups: rec.photo.equipment.medium-format
Subject: HASSELBLAD VACUUM FILM BACK
Date: 1 Jun 2003
Hi guys,
any news about the new vacuum magazines for Hasselblad? Can anybody
provide me with a link to the new product?
Thanks,..Bernard
From: Q.G. de Bakker [qnu@tiscali.nl]
Sent: Tue 6/17/2003
To: hasselblad@kelvin.net
Subject: Re: [HUG] FILM FLATNESS OF 120 + A-12 Spacing problem?
Tom Christiansen wrote:
> As the article says:
> "Since the photographer cannot alter the geometry and mechanics of his
> camera, he can only influence the other factor: time. A film run through
> the camera without much time between exposures should result in good
> flatness and hence sharpness. Five minutes between exposures may be some
> sort of limit, depending on brand and type of film. 15 minutes are likely
> to show an influence of bending around rollers. Two hours definitively
will.
The puzzling part about this is that film, both 120 and 220, is not only
allowed to rest bent around rollers for some time, but that no matter how
fast you shoot, it has been bent around the spool it comes on for some
considerable period, definitely much longer than the 15 minutes Zeiss
recommend as maximum.
Using a straight path back, like the Rollei's, one would assume that
transporting the film after each exposure, and then allowing some time (say
15 minutes or more) for the fresh film in the gate to straighten out, get
rid of its spool-induced curl, would be better. But there's no mention of
that in Zeiss' report.
Even in the backwards bending film path like the one in Hasselblad backs,
allowing the film to 'uncurl' in the film gate, helped by the pressure
plate, would be better than using the bit that just came of a tightly wound
spool, not so?
;-)
Funny though that Hasselblad once (more than 50 years ago now) claimed that
the "double back" type filmpath they used, in conjunction with the careful
positioning of rollers in shell and insert relative to each other (hence the
matched shells and inserts), would ensure better film flatness than the
"straight path" type filmbacks. A patent was awarded, honouring this claim.
Shows how easy it is to get something patented?
From: Tom Christiansen [tomchr@softhome.net]
Sent: Tue 6/17/2003
To: hasselblad@kelvin.net
Subject: RE: [HUG] FILM FLATNESS OF 120 + A-12 Spacing problem?
Hi,
>Better flatness by a factor of 2 ? Does that mean? Twice as flat?
Yes. According to the article, they measured film height as a function of
position on the film plane. The film flatness is then expressed as the
deviation between minimum film height (flat against the plane) and max film
height. I would think that if film flatness, delta_h = max - min, then
delta_h for 120 is twice that of 220. Hence, 220 is twice as flat.
>So do you think if you were not using a motor drive body or accessory and
>you got the film in the film back and out of the film back in thirty
>minutes, exposing all twelve frames on an A-12 film back, do you think
>there would be any difference on an enlargement of that photo? ....
As the article says:
"Since the photographer cannot alter the geometry and mechanics of his
camera, he can only influence the other factor: time. A film run through
the camera without much time between exposures should result in good
flatness and hence sharpness. Five minutes between exposures may be some
sort of limit, depending on brand and type of film. 15 minutes are likely
to show an influence of bending around rollers. Two hours definitively will.
As a rule of thumb: For best sharpness in medium format, prefer 220 type
roll film and run it through the camera rather quickly."
The article is available at:
http://www.zeiss.de/C12567A8003B58B9/allBySubject/134AEE504E89CD50C12569620039712C
If the link doesn't work for you, cut 'n' paste it into your browser or
search for "zeiss film flatness" (without the "") on www.google.com. It's
the first link that shows up in the list.
Regarding fogging of film: Change film in a shaded area. At the very least
use your own shadow to protect the film from the light. Also make sure that
the film back winds the film tightly on the spool. I used to shoot with a
Contax 645 and it didn't wind the film up too tightly. So if you weren't
careful, you could actually squeeze the roll of film into an oval, thus,
exposing the edges of the film to daylight. I've had a few images at the
end of a roll which were fogged along the edge for that reason. I have not
had this happen on my Hasselblad A-24 back.
Tom
[Ed. note: note errors in registration to one side...]
Date: Thu, 18 Sep 2003
From: dave passmore davepdawg@aol.com
Subject: [Russiancamera] Re: adjusting lens register
To: Russiancamera-user russiancamera-user@mail.beststuff.com
Bruce,
I agree with Dave, if you paid yourself a dollar an hour using the
sighting method ,you would soon see the value of used calipers!Go to one of
the chain pawn shops in your town or ebay. You can get precesion Brown and
Sharp or Starret depth mic's for 25-35 bux.I got Brown and Sharps for 17
dollars.Much faster and more accurate than sighting.The sighting method will
work but lets say you viewed and saw that a camera was off a little. how
much do you move the flange in or out? It would take many times trial and
error installing varoius shims to sight it right.Plus, Ive found on mine
that the flanges only need shimming to one side,this has occured on every
one ive done so far.Its much easier and more precise to measure with a
micrometer and find out that you need 2 thousandths. Now a shim can be made
and installed. Plus the micrometer would find other uses over the years.I am
not discounting the sighting method you suggested,its just that time and
frustration are a player here........Good luck,Dave
From: qnu@tiscali.nl (Q.G. de Bakker)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Making the jump
Date: 27 Oct 2003
Frank Pittel wrote:
> [...] If film flatness
> is still an issue you can use double sided tape to stick the film to the
> holder. :-)
Just in case someone is fooled by the ":-)" in the sentence above,
this actually is the trick employed. When film flatness becomes a
problem, low tack adhesive film holders are indeed the solution.
The regular sheet film holders will not do, since to load these you
have to slide the film in, which won't work very well when the holder
is sticky. You can buy holders (expensive) or make them yourself.
Brian Reynolds
From: Ming-Sung Lin sherfied@ms8.hinet.net
Subject: Re: [Rollei] Bill Maxwell, Sharpness Issues
From: "Rainey, William" william.rainey@msfc.nasa.gov
Subject: RE: [BRONICA] Re: bronica-digest V1 #31
From: karel.sotek@infineon.com
To: hasselblad@kelvin.net
Subject: Hasselblad focusing accuracy
Karel Sotek
Date: Fri, 17 Sep 1999
From: Chris Lee chrislee1@home.com
Subject: Re: [Rollei] Contax 645 off topic (but Zeiss lenses!!)
> I just questioned them on the phone.
>WRONG!!!!!
>Glad I checked!!! The deal was that wide open their results were not good which
>he attributed to film flatness and AF issues. NOT THE GLASS.
> But the end result was that the effect of the Contax/Zeiss 645 imaging system
>did not wow them away from their Pentax 645 which they find sharper than Mamiya
>for what that is worth.
>I call up Herr Zeiss and offer to mow his lawn for a month.
> Mark Rabiner
Newsgroups: rec.photo.equipment.35mm
Subject: Re: film flatness effects page URL Re: Lens barrel 'slop' and
sharpness
Date: 28 Nov 1999
>Film flatness is surprisingly critical in determining the overall camera
>performance (snip)
>and lens misalignment can have similar problems.
HRphotography
http://hometown.aol.com/hrphoto/myhomepage/business.html
Date: Mon, 29 Nov 1999
From: Paul van Walree walrusjr@hetnet.nl
[update: Paul van Walree info@vanWalree.com http://www.vanWalree.com/]
Subject: Re: film flatness effects page URL Re: Lens barrel 'slop' and
sharpness
> Film flatness is surprisingly critical in determining the overall camera
> performance - especially lens resolution or sharpness (as measured by
> lpmm) and lens contrast. As we will see below, film often buckles in 60%
> of 35mm SLRs tested, and virtually all medium format backs - by an average
> of 0.2mm (on 35mm). Yet even a 0.08mm film bulge can reduce contrast by an
> astonishing 48%! That same 0.08mm film bulge could well be outside the
> depth of focus of a typical 50mm lens at f/8 (0.064), let alone at f/4
> (0.016mm) or faster.
W.
Newsgroups: rec.photo.equipment.35mm
Subject: Re: film flatness effects page URL Re: Lens barrel 'slop' and
sharpness
Date: Sun, 28 Nov 1999
Newsgroups: rec.photo.equipment.35mm
Subject: Re: film flatness effects
Date: Mon, 29 Nov 1999
Anders Svensson
Anders.-.Eivor.Svensson@swipnet.se
Date: Sat, 05 Feb 2000
From: Phil Stiles pjs@worldpath.net
Subject: [Rollei] Lens sharpness
Date: Sat, 29 Jan 2000
Newsgroups: sci.astro.amateur
Subject: Re: Focusing for Photography
> 3) The human eye can accomodate to a range of apparent "correct"
> focusing points. This kind of slack is usually covered over by the
> depth of field in most commonly used lenses but a typical telescope,
> with its fixed aperture and very small depth of field, will reveal this
> error. About the only truly reliable way to get around this is to use a
> Foucault focusing technique, i.e. a knife-edge focuser. That's why
> devices like the Spectra Astrosystems Sure Sharp were developed. If it
> wasn't for the problem in 1) described below which I know my particular
> OM-1 suffers from, a Hartmann mask (scope cover with two or more holes
> punched in it) used on a bright star would be considerably easier.
>
> Mike
> http://www.concentric.net/~richmann/
>
> frostycat@my-deja.com wrote:
> >
> > Suggest two possibilities:
> >
> > 1) You may not really be focused. Often the focusing screen on SLRs
> > are not par-focal with film plane. I have Nikon F3, N90S, and F5
> > can tell you none of these focusing screens are parfocal. This becomes
> > more and more critical as focal length increases. There are focusing
> > aids available so that you can be certain of precise focus. However,
> > since you say you are getting good results at 800mm this may not be
> > it.
> >
> > 2) As focal length increases effects of mirror slap and shutter shake
> > can increase. From your description, the only component left would be
> > the shutter. At the focal lengths above 800mm even this can be very
> > troublesome and hard to get rid of. Worst ranges are typically 1/125th
> > out to 1 second or so -- probably the range you are using for the
> > moon. This is VERY difficult to eliminate. Best solutions I've found
> > involve 1) separate support for the camera body -- really tricky for
> > moving subject like the moon. 2) choose another film speed or stop
> > down the scope to get yourself out of the 1/125 to 1 sec shutter
> > range. 3) Use another camera body. All the shutters have different
> > "shakes" and a different body may help. 4) Take LOTS of identical
> > exposures. The shutter doesn't cause vibration the same way every
> > time. You may find one in your series of identical exposures that is
> > less affected or unaffected. 5) Some people use the "hat-trick" where
> > they cover the objective with a dark barrier, open the shutter, remove
> > the barrier to make the exposure, then cover again and close the
> > shutter all without touching the set-up. Works well but very, very
> > difficult to time precisely with large aperture and times under five
> > seconds or so.
> >
> > Hope some of this helps. It know its aggravating.
> >
> > dvstuart@my-deja.com wrote:
> > > Hello:
> > >
> > > Can someone explain why I can't seem to take an in-focus photograph
> > when
> > > I attach my SLR to my Ultima 8 via a T-adapter? I use a matte screen
> > on
> > > my old F-1, and everything looks good when I shoot. I also lock up
> > the
> > > mirror, use a cable shutter release and turn off the U-8 motor drive
> > to
> > > minimize vibration and shake. My photo target is the moon, and I have
> > > great luck with my 800mm photo lens on the same camera.
> > >
> > > What's going on?
> > >
> > > Thanks,
> > >
> > > Dan
> --
> Mike
Date: Mon, 7 Feb 2000
From: Tim Ellestad ellestad@mailbag.com
Subject: Re: [Rollei] Re: Lens Sharpness Problem
><
ellestad@mailbag.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Are Leica lenses really better? (Of course!)
Date: 21 Feb 2000
f1= 1 micron
f2= 4 microns
f4= 16microns
f8= 64 microns.
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Are Leica lenses really better? (Of course!)
Date: 22 Feb 2000
2 students under 10 microns
4 students 15 microns error
7 studenst 20 microns error
6 students 30 microns error
5 students 40 microns error
3 students 50 microns error
2 students 60 microns error
1 student 70+ microns error
From: "Schnickelfritz V." super_furby_nojunk@junkno_hotmail.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Flattening rollfilm
> After I get my 120 rollfilm developed, it's all curled up, which makes it
> difficult to put in my transparency scanner. Does anyone have any handy
> hints on flattening film?
>
> Chuck
Date: Sat, 20 Nov 1999
From: Kip Babington cbabing3@swbell.net
Subject: [Rollei] in re slight out of focus at infinity
Kip
> In the absence of a collimator, the thing to do is put a ground
> glass on the back of the camera and check focus against the
> viewing lens at a variety of distances. If focus in both lenses
> agrees, then it does not matter that the focus goes slightly
> past infinity. Focus should be determined visually, even at
> infinity, rather than depending on rack stops.
>
> If the lenses agree and this bothers you, you could have a
> repairman set the visual infinity to correspond to the focusing
> knob. I would only worry if the two lenses do not agree on
> focus.
>
> Bob
Date: Sun, 19 Mar 2000
From: Mike Johnston michaeljohnston@ameritech.net
Subject: [Leica] Film flatness
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: RB-67 Focusing Is Off?
Date: Sun, 19 Mar 00
>Where do you get "70% of all" and what is the mirror to film relationship?
Date: Sun, 19 Mar 2000
From: "Henning J. Wulff" henningw@archiphoto.com
Subject: RE: [Leica] 35mm versus 120
>That makes NO sense. I know dozens of VERY experienced MF shooters, as
>well as I am certainly one, and I do nothing 'special' to 'keep my film
>flat'.
>
>What, exactly, do 'experienced MF shooters' DO to supposedly keep the film
>flat?
>
>Just as a note, THE bible on Hasselblad photography, called "The Hasselblad
>Manual" only references 'film flatness' in ONE statement on matching the
>backs with the inserts. If this were truly a problem, and if 'experienced
>MF shooters' actually did 1) have a problem with film flatness, and 2)
>actually did something about it, it would be mentioned in this book.
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com
Date: Sun, 19 Mar 2000
From: Paul Roark proark@silcom.com
Subject: Re: [Leica] 35mm versus 120
>...
>But what do experienced MF shooters do to keep their film flat?
>
>Paul Roark wrote:
>
>> Experienced medium format shooters learn how to keep the film flat. 35
>> film will also not lie flat where it has been pinched by the film can too
>> long.
http://www.silcom.com/~proark/photos.html
Date: Sun, 19 Mar 2000
From: "Henning J. Wulff" henningw@archiphoto.com
Subject: [Leica] Film flatness and other mumblings
>Is it disposable?
>
>Dan C.
>
> Jerald Rosenfeld wrote:
>>I just checked it is Sinar that has a film holder for 4x5 camera ONLY
>>$765 FOR ONE HOLDER. They do assume that the film will be flat. THAT
>>BEING 2 SHEETS OF FILM.
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com
Date: Mon, 20 Mar 2000
From: William Carson ke7gm@earthlink.net
Subject: [Leica] Re: Leica Users digest V16 #54
Date: Mon, 20 Mar 2000
From: Paul Roark proark@silcom.com
Subject: [Leica] image quality and format/ 35 v. 120
>> [Paul Roark wrote] (Moreover, that Fuji GA645 Zi zoom is, in some ways,
>>better than my Zeiss glass -- amazing.)
> [Austin Franklin wrote] I have that camera, and I do not concur. It IS
>nice, but hardly a match
>for my Zeiss Hasselblad lenses, ...
http://www.silcom.com/~proark/photos.html
From: "S. Sherman" flexaret@sprynet.com
To: bronica@ilist.net
Subject: Re: film flatness URL was Sam Sherman Re: [BRONICA] Medium Format
>From: Robert Monaghan rmonagha@post.cis.smu.edu
>To: bronica@iList.net
>Subject: film flatness URL was Sam Sherman Re: [BRONICA] Medium Format
>Date: Mon, Nov 1, 1999
>
>see http://www.smu.edu/~rmonagha/mf/flat.html Film Flatness Pages for some
>further details and factoids and related info; I tend to agree that it is a
>problem which gets disguised as focusing errors but is inherent in most
>designs, with a few such as the Kowa 66 as major exceptions... regards bobm
Date: Mon, 20 Mar 2000
From: "Bob Parsons" bobp@dodo.demon.co.uk
Subject: Re: [Leica] Re: 35mm versus 120
Date: Mon, 20 Mar 2000
From: "Henning J. Wulff" henningw@archiphoto.com
Subject: Re: [Leica] Re: Leica Users digest V16 #54
>Regarding "Film Flatness": It would appear that the people at Franke &
>Heidecke in Braunschweig encountered the problem of "film flatness" quite
>a long time ago in
>their engineering of the Rollei cameras. At least two models of their 2¼"
>square format reflex cameras [I owned a Rollei flex F and also a
>Tele-Rolleiflrx with
>this feature] offered optical flat glass plates located in the image
>plane, ahead of the film, to offset the tendency of the 120 film to "bow"
>or "buckle-out" in
>it's location in the aperture of the image-making portion of the cameras.
>It appears that the pressure plate by itself in a single plane did not
>correct the
>geometry of the film in this critical area. It is reasonable that the
>film would present a very flat surface to the image with this feature. I
>do not know that
>Hasselblad ever offered such a feature although it is certainly reasonable
>to assume that their engineers would aware of this design? Bill Carson,
>KE7GM@earthlink.net
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com
Date: Tue, 21 Mar 2000
From: "Raimo Korhonen" raimo.korhonen@pp2.inet.fi
Subject: Vs: [Leica] Re: Leica Users digest V16 #54
Date: Thu, 23 Mar 2000
From: bigler@jsbach.univ-fcomte.fr
Subject: [Rollei] image quality and glass plate
Emmanuel BIGLER
bigler@lpmo.univ-fcomte.fr
Date: Fri, 24 Mar 2000
From: carter rollei@mpdevinc.com
Subject: Re: [Rollei] image quality and glass plate
>> For hte SL 2000/3003 magazines Rolleis sells a
>> separate film pressure plate
>> especially for the
>> TEchnical Pan
>
> Huh??!! Wha...? Is this a joke? If it isn't, then
>there IS one born every minute.
DeepInTheHeartOfaNortheastAtlantaSuburb...
Date: Sun, 31 Oct 1999
From: "S. Sherman" flexaret@sprynet.com
To: bronica@ilist.net
Cc: idcc@kjsl.com
Subject: [BRONICA] Medium Format Focus at Photo Plus Expo- New York
to: IDCC
Date: Thu, 1 Jan 1970
From: greg_jones@mk.com
Subject: [Rollei] Rollei TLR filmbacks
-Greg Jones
Date: Fri, 24 Mar 2000
From: Richard Urmonas rurmonas@ieee.org
Subject: Re: [Rollei] image quality and glass plate
Richard Urmonas
rurmonas@ieee.org
Date: Tue, 21 Mar 2000
From: InfinityDT@aol.com
Subject: Re: Field Curvature
Date: Fri, 31 Mar 2000
From: Clive Warren Clive.Warren@src.bae.co.uk
Subject: Re: [KOML] Getting out of the KO biz
Date: Thu, 23 Sep 1999
From: "S. Sherman" flexaret@sprynet.com
To: rmonagha@post.cis.smu.edu
Subject: Film Flatness - Mamiya
From: "Info@Mamiya" danc@mamiya.com
To: flexaret@sprynet.com
Subject:
Date: Thu, Sep 23, 1999
Mamiya America Corp
8 Westchester Plaza
Elmsford, NY 10523
(914)347-3300
info@mamiya.com
From: Geoffrey Semorile info@cameratech.com
To: bronica@iList.net
Subject: RE: [BRONICA] Film Back Light Leaks
>>Well, let's not take the comparison between MF and PNS too far. Of
course
>>the medium format camera produces infinitely sharper images - and if the
>>frames don't overlap one another you might have something saleable.
>
>
>
>Might ? Try to sell something from a P&S :) I have had zero
>frame overlapping on _any_ of my Bronicas. I did have that
>problem on my RZ, and my Hasselblad.
>
>Regards,
>
>Tim
2308 Taraval St. S. F., CA 94116 USA
UNDERWATER PHOTO/VIDEO SALES-REPAIRS-RENTALS
(415) 242-1700 Fax (415) 242-1719
email: info@cameratech.com web site: http://www.cameratech.com
Date: Thu, 15 Jul 1999
From: todd todd_belcher@bc.sympatico.ca
Subject: Re: [Rollei] 3.5F type 3 W/O Flat Glass
Date: Tue, 11 Apr 2000
From: "Bob Shell" bob@bobshell.com
Subject: Re: [CONTAX] 220 vacuum back
>From: John Coan jcoan@alumni.duke.edu
>To: contax@photo.cis.to
>Subject: Re: [CONTAX] 220 vacuum back
>Date: Tue, Apr 11, 2000, 2:30 PM
>
> Bradley,
> I never got one because like you, I didn't see how it could improve things
> very
> much. Stop down a few stops and the DOF should take care of any film
> flatness
> problems.
Date: Tue, 11 Apr 2000
From: "bradley hanson" bradley.hanson@home.com
Subject: [CONTAX] 220 vacuum back
Seattle, WA
http://www.hansonphotography.com
From: adcmail!briang@uu4.psi.com (Brian Godfrey)
Date: Tue, 30 Mar 93
Subject: Re: Medium Format Digest Vol 2, No. 22
>From: jmaio@arcserv.dasd.honeywell.com (John Maio)
>Date: Fri, 26 Mar 93
>Subject: Mamiya 645 film tensioning
>
>Has anyone notices a problem with loose film tension on the Mamiya
>645 inserts? I have a 645 super and notices that some rolls were
>not tightly wound after exposure, allowing light leaks and fogging
>along the edges of some frames - even into the image occasionally.
>
>I asked Mamiya about it and they said I had to be careful about
>making sure the supply reel has tension on it (via my thumb) when
>I first load the take-up reel, else the film will not be tight during
>exposure (wouldn't lie flat) and would also result in the loosely
>wound situation I described. Is there a technique you use to load the
>insert that isn't apparent?
atlastele.com
From: Andrew Cassino andyc@lsid.hp.com
Date: Tue, 11 May 93
Subject: Re: Medium Format Digest Vol 2, No. 31
andyc@hplsla.hp.com
From: Tim Takahashi tim@me.rochester.edu
Date: Wed, 2 Mar 94
Subject: Film Flatness Issues
From: troby@carl.org (Thorn Roby)
Date: Wed, 9 Mar 1994
Subject: Re: Roll Back Film Flatness
From: stephan miller smiller@world.std.com
Date: Wed, 9 Mar 1994
Subject: Re: Film Flatness Issues
From: Peter Ochmann ochmann@mpie-duesseldorf.mpg.d400.de
Date: Tue, 15 Mar 1994
Subject: Film flatness
ochmann@pmhp1.mpie-duesseldorf.mpg.de
From: "Brian Campbell" thebrain@intergate.bc.ca
To: pentax-discuss@discuss.pentax.com
Date: Mon, 1 May 2000
Subject: Film Flatness
Brian
Date: Mon, 1 May 2000
To: pentax-discuss@discuss.pentax.com
From: paal@norvol.hi.is (Pål Jensen)
Subject: Re: Film Flatness
>Since I shoot at wide open quite a bit and notice that some of my
>images appear to be in-focus in areas of the frame and out of focus
>in other areas of the same frame, this would seem to be one cause
>of the problem. With the lenses trying to focus an image onto a
>theoretically flat plane, any deviation in that "flatness" would cause
>the out-of-focus areas that I believe are appearing.
>My question is this: Is there anything that can be done about this?
>Send the cameras back to Pentax for a pressure plate adjustment?
>The article mentioned pieces of glass in front of the film and vacuum
>film holders (for MF) but I have never heard of anything like that for
>35mm.
From Contax Mailing List:
Date: Mon, 01 May 2000
From: "Bob Shell" bob@bobshell.com
Subject: Re: [CONTAX] The Contax decision
> "Holy Price Tag, Batman!"
>
> Thought it might be interesting, and informative to anyone lurking to learn
> more about Contax, as to what made us decide to go with Contax equipment.
> Contax vs Nikon vs Canon vs Minolta vs Leica vs Olympus vs etc.
>
> I'll kick off my own experience, and perhaps others will join in.
From: "Don Williams" don.williams@kolumbus.fi
To: pentax-discuss@discuss.pentax.com
Subject: Repeat of comments about film flatness in 120/220 rollfilm
backs
Date: Fri, 5 May 2000
Mamiya 6x4.5, 6x7 and 6x8 - 120 and 220,
Linhof Super-Rollex 6x6, 6x7 and 6x9 - 120, 220 and 70mm.
Date: Fri, 5 May 2000
From: Tim Ellestad ellestad@mailbag.com
To: rollei@mejac.palo-alto.ca.us
Subject: Re: Re: [Rollei] 6003 vs. 6008 backs
ellestad@mailbag.com
From: austin@darkroom.com austin@darkroom.com
Date: Friday, May 05, 2000
Subject: Re: Re: [Rollei] 6003 vs. 6008 backs
>Technically, I agree. I also understand one can measure the film flatness,
>and note one method is 'flatter' than another, and obviously some mechanical
>accommodations can be made to make the film 'more flat', but whether it
>actually makes a real discernable difference in the resultant image is the
>real question.
>
>From what I have tested my self, and others tests I have seen, the
>answer, under 'normal' circumstances is, no, not with a 2 1/4 negative.
>
>
>
>>
>>The best ones are the vacuum backs. The only one that uses easily
>>available 220 film is the new one for the Contax 645. This should
>>give the flattest film yet and show off those fast new Zeiss lenses
>>to maximum advantage.
>>
>>Bob
>>>From: austin@darkroom.com
>>>To: rollei@mejac.palo-alto.ca.us
>>>Subject: Re: Re: [Rollei] 6003 vs. 6008 backs
>>>Date: Fri, May 5, 2000, 3:29 PM
>>>
>>
>>> That's all nice, but is there any proof in the resultant images, that
>>> demonstrates one is better than the other, or that it even matters?
Date: Fri, 5 May 2000
From: calciua@hn.va.nec.com
To: rollei@mejac.palo-alto.ca.us
Subject: Re: [Rollei] 6003 vs. 6008 backs
Andrei D. Calciu
NEC America, Inc.
Date: Fri, 05 May 2000
From: Bob Shell bob@bobshell.com
To: rollei@mejac.palo-alto.ca.us
Subject: Re: [Rollei] 6003 vs. 6008 backs
>From: ARTHURWG@aol.com
>To: rollei@mejac.palo-alto.ca.us
>Subject: Re: [Rollei] 6003 vs. 6008 backs
>Date: Fri, May 5, 2000, 2:00 PM
>
> I think that "bending the film around," like with Hasselblads, is exactly
> what makes the film lie flat.
Date: Fri, 5 May 2000
From: "Kotsinadelis, Peter (Peter)" peterk@lucent.com
Reply to: rollei@mejac.palo-alto.ca.us
Subject: RE: [Rollei] 6003 vs. 6008 backs
From: ARTHURWG@aol.com [mailto:ARTHURWG@aol.com]
Sent: Friday, May 05, 2000 11:01 AM
To: rollei@mejac.palo-alto.ca.us
Subject: Re: [Rollei] 6003 vs. 6008 backs
Date: Fri, 5 May 2000
From: rlb rlb@triad.rr.com
To: rollei@mejac.palo-alto.ca.us
Subject: Re: [Rollei] 6003 vs. 6008 backs
Date: Sat, 06 May 2000
From: Bob Shell bob@bobshell.com
Subject: Re: [Rollei] film flatness/6003 vs. 6008 backs
>From: ARTHURWG@aol.com
>To: rollei@mejac.palo-alto.ca.us
>Subject: Re: [Rollei] film flatness/6003 vs. 6008 backs
>Date: Fri, May 5, 2000, 8:25 PM
> When the film comes off the spool it is concave; when it bends around, as in
> the Hasselblad, it becomes flat. You don't have to believe me. Have a look
> for yourself.
Date: Sat, 06 May 2000
From: Bob Shell bob@bobshell.com
Subject: Re: [Rollei] 6003 vs. 6008 backs
> Isn't there a 220 vacuum back for the 6000 series Rolleis?
Date: Sat, 06 May 2000
From: Bob Shell bob@bobshell.com
Subject: Re: [Rollei] film flatness/6003 vs. 6008 backs
>From: Austin Franklin austin@darkroom.com
>Subject: RE: [Rollei] film flatness/6003 vs. 6008 backs
>Date: Sat, May 6, 2000, 11:17 AM
>
>> ...gimmicks
>
> "gimmicks"? The result of engineering is "gimmicks"? That's quite
> condescending.
>> Film flatness is a major problem with rollfilm cameras.
>
> "MAJOR problem"? Come on. You are blowing this way way out of proportion.
Date: Sat, 06 May 2000
From: Bob Shell bob@bobshell.com
Subject: Re: [Rollei]film flatness/was 6003 vs. 6008 backs
>From: ARTHURWG@aol.com
>To: rollei@mejac.palo-alto.ca.us
>Subject: Re: [Rollei]film flatness/was 6003 vs. 6008 backs
>Date: Sat, May 6, 2000, 4:30 PM
>
> OK, Bob, what's the Hasselblad secret? Hassie pictures look pretty flat to
> me, but maybe I'm missing something.
Date: Sun, 07 May 2000
From: Bob Shell bob@bobshell.com
Subject: Re: [Rollei] Film Flatness
>From: Austin Franklin austin@darkroom.com
>Subject: RE: [Rollei] Film Flatness
>Date: Sat, May 6, 2000, 10:57 PM
> Minox cameras up through the late B models have a curved film plane.
>
> They obviously have allowed for curvature. I am not saying this has
> anything to do with the Nikon claim, but the point is, you can allow for
> curvature in your lense design, that is, if you are a lense designer ;-)
Date: Sun, 07 May 2000
From: pjs pjs@worldpath.net
Subject: [Rollei] film flatness, Rollei, et al
Date: Sun, 07 May 2000
From: Bob Shell bob@bobshell.com
Subject: Re: [Rollei] film flatness, Rollei, et al
>From: pjs pjs@worldpath.net
>To: rollei@mejac.palo-alto.ca.us
>Subject: [Rollei] film flatness, Rollei, et al
>Date: Sun, May 7, 2000, 3:15 PM
>
> My memory of Bill's method is that he uses film in the
> camera, and takes a spot about a third out from center, as a good
> average point.
Date: Sun, 7 May 2000
From: Guido Cova gcova@leosh.com
Subject: R: [Rollei] Film Flatness
Guido
Date: Mon, 08 May 2000
From: Bob Shell bob@bobshell.com
Subject: Re: R: [Rollei] Film Flatness
>From: "R. J. Bender" rjbender@apci.net
>To: rollei@mejac.palo-alto.ca.us
>Subject: Re: R: [Rollei] Film Flatness
>Date: Sun, May 7, 2000, 7:01 PM
> Rapid and Koni Omega 6X7 cameras had a retracting pressure plate:
> http://www.skypoint.com/members/jcwatne/omega/page16.jpg
> http://www.skypoint.com/members/jcwatne/omega/page07.jpg
Date: Sun, 07 May 2000
From: "Bob Shell" bob@bobshell.com
Subject: Re: [Rollei] Film Flatness
>From: Austin Franklin austin@darkroom.com
>Subject: RE: [Rollei] Film Flatness
>Date: Sat, May 6, 2000, 10:57 PM
> Minox cameras up through the late B models have a curved film plane.
>
> They obviously have allowed for curvature. I am not saying this has
> anything to do with the Nikon claim, but the point is, you can allow for
> curvature in your lense design, that is, if you are a lense designer ;-)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: what is a vacuum insert?
Date: Wed, 03 May 2000
> What is the difference between a film insert and a vacuum insert? ...why
> (and when) would someone use one over the other?
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: what is a vacuum insert?
Date: Wed, 03 May 00
>Doug Spencer at
>limepix@home.com wrote:
>
>> What is the difference between a film insert and a vacuum insert? ..why
>> (and when) would someone use one over the other?
>
>A vacuum insert is for 220 film it allows the film to be sucked to the
>shutter, resulting in flat film plane, It doesn't work with 120 as that it
>has paper backings, unfortunately 220 are being phased out by manfacturer
>now. As far as I know, it is available for contax 645 only,
Bye,
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: what is a vacuum insert?
Date: Thu, 4 May 2000
> The 70mm back for Mamiya RB (and possibly Hassy, if only the rare long-roll
> back) also have a vacuum pressure plate. [...]
From Leica Mailing List:
Date: Thu, 18 May 2000
From: "Henning J. Wulff" henningw@archiphoto.com
Subject: RE: [Leica] Noctilux viewfinder blocking
>--
>
> Peterson Arthur G NSSC wrote:
>>
>>I don't know, and so can only presume John is right, that the "M rangefinder
>>is more accurate than a SLR at 50mm." But my question is this: given the
>>fact that with an SLR one is actually looking through the lens at (almost
>>always) full aperture, does it not then stand to reason that an SLR would be
>>able to focus any lens, of whatever focal length and whatever maximum
>>aperture, with sufficient accuracy for that particular lens? I'm not being
>>argumentative, just asking what seems like a reasonable question.
>
>But the accuracy of the M system is fixed by the width of the two
>viewfinder ports. As the lens gets faster/longer, it (the margin of error)
>becomes too great to focus within the DOF of the lens. In other words,
>with an f/1.0 lens, the SLR is probably a little better.
- --------------
Focal length Max aperture Max aperture Max aperture
M3 M2, M4, M5, M6 M6HM, M6J
21mm 0.12 0.15 0,13
24mm 0.15 0,19 0,16
28 mm 0.21 0.26 0,22
35 mm 0.33 0.41 0,35
50 mm 0.67 0.84 0,71
75 mm 1.5 1.88 1,59
90 mm 2.17 2.71 2,29
135 mm 4.88 6.1 5,16
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com
Date: Fri, 19 May 2000
From: "Bob Shell" bob@bobshell.com
Subject: Re: [CONTAX] [OT] Canon Eos D32
>To: contax@photo.cis.to
>Subject: Re: [CONTAX] [OT] Canon Eos D32
>Date: Fri, May 19, 2000, 12:52 AM
>
> And, as some lense engineers
> have suggested, if Zeiss' Planars produce 30% to 40% more information
> than the next best level of pro lense manufacturer's, can you imagine
> what detail and dimensionality and color Zeiss digital images would
> offer beyond anything that even our most wonderful silver halide has
> ever revealed thus far? With a primary digitally captured image/file,
> the potential image would far outstrip even the very best film and pro
> level scanner digitization, imo.
Date: Fri, 19 May 2000
From: be1ben@netzero.net
Subject: Re: [CONTAX] [OT] Canon Eos D32
> There is something about this in the latest Zeiss newsletter.
> Basically it says that lenses have not been as good as they could
> be due to the fact that film simply did not lie flat enough to
> make it worth the lens designer's while to spend the time correcting
> for flatness. Since digital sensor chips are VERY flat, this offers
> the lens designers an opportunity to really show off what they can
> do.
Date: Thu, 29 Jun 2000
From: "Bob Shell" bob@bobshell.com
Subject: Re: [CONTAX] Re: Hexar RF(was way OT)
Date: Thu, 06 Jul 2000
From: Clive Warren Clive.Warren@baesystems.com
Subject: Re: [KOML] 58mm image circle - coverage for movements
>johnstafford wrote:
>>
>> I have similar reservations regarding film flatness. Some people are
>> experimenting with the US Navy surplus "Torpedo Camera" back, but it seems a
>> hassle to adapt it to 220/120 spools.
>
>Another approach that I've heard for cheap MF panaroma is to get one
>of the really old folders that takes some big goofy film size that is
>no longer made, make adaptors to hold 120 film, and put edge holders
>or some sort of mask on.
>The problems with this approach are:
>1) Film flatness - manageable if you have the resources.
>2) Hard to find cameras.
>3) Old lenses are usually not so great, typically 2-3 element
> uncoated.
>
>But they are cheap.
>
>Regards,
>--
>Martin F. Melhus
Photographic Services, Filters and Equipment,
Infrared FAQ
Newsgroups: rec.photo.equipment.large-format
Subject: Re: LF lenses - MF lenses comparison
Date: Tue, 11 Jul 2000
> (Although they measure well, I sometimes wonder if the problem isn't that the
> Graflex backs do a poor job of keeping the film flat ...
Newsgroups: rec.photo.equipment.large-format
Date: Tue, 11 Jul 2000
Subject: Re: LF lenses - MF lenses comparison
>peter kessler pkessler@odn.de wrote:
>
>> Some high-quality lenses as the Super-Angulon from Schneider or the
>> famous lenses made by Zeiss as the Biogon, Planar etc.
>> where aviable for MF as for LF cameras.
>> Of course with different shutters etc., but the lenses are the same.
>>
>> So the image quality is the same.
>
>You are not suggesting, are you, that one merely has to 'scale up' a very
>good MF lens to cover LF and the lens will be equal in terms of optics
>(resolution, aberration control) as the original MF are you? Because that is
>dead wrong. Lens designs tend to scale down well, but not up. (If they did
>scale up, we'd have the ridiculous but common prospect of LF lenses
>resolving far more than can practically be used.)
Richard Knoppow
dickburk@ix.netcom.com
Date: Wed, 21 Jun 2000
From: Richard Knoppow dickburk@ix.netcom.com
Subject: Re: [Rollei] Oh, no, not Planar vs. Xenotar!
>----- Original Message -----
>From: Bob Shell bob@bobshell.com
>Sent: Wednesday, June 21, 2000 10:13 AM
>
>> Zeiss says in their literature that the Planar is designed for a flat
>> field, thus its name.
>>
>> Bob
>
>I remember that - but didn't Schneider also claim that the Xenotar had a
>flatter field than earlier lenses?
>
>(BTW - I should add, in case anyone is wondering, that I am not suggesting
>that the Planar is better than the Xenotar (or vice versa). I am just
>curious about what you might call the "signature" or "character" of the
>two lenses.)
>
>Gary Toop
>
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
From Rollei Mailing List:
Date: Mon, 07 Aug 2000
From: Bob Shell bob@bobshell.com
Subject: Re: [Rollei] 120/220 film flatness
Date: Mon, 07 Aug 2000
From: Richard Knoppow dickburk@ix.netcom.com
Subject: Re: [Rollei] 120/220 film flatness
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
Date: Mon, 07 Aug 2000
From: Gene Johnson genej2@home.com
Subject: Re: [Rollei] 120/220 film flatness
Date: Mon, 7 Aug 2000
From: Robert Monaghan rmonagha@post.cis.smu.edu
Subject: Re: [Rollei] 120/220 film flatness
From: Bruce McLaughlin bmclaugh@primenet.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: 35mm or Medium Format
Date: Sat, 05 Aug 2000
From: "S. Sherman" flexaret@sprynet.com
To: rmonagha@post.cis.smu.edu
Subject: FILM FLATNESS ISSUES
Date: Mon, 07 Aug 2000
From: Bob Shell bob@bobshell.com
Subject: Re: [CONTAX] 120/220 film flatness
Date: Mon, 07 Aug 2000
From: Bob Shell bob@bobshell.com
Subject: Re: [CONTAX] 120/220 film flatness
> From: Alexander mediadyne@hol.gr
> Reply-To: contax@photo.cis.to
> Date: Tue, 08 Aug 2000
> To: contax@photo.cis.to
> Subject: Re: [CONTAX] 120/220 film flatness
>
> That's why the vacuum pressure plate was the smartest thing they designed!!!!
> It avoid all that!
> And I dont see it in the N1.
Date: Mon, 7 Aug 2000
From: ShadCat11@aol.com
Subject: Re: Re: [Rollei] 120/220 film flatness
Date: Mon, 7 Aug 2000
From: r u contaxaholic@yahoo.com
Subject: Re: [CONTAX] Contax or Hasselblad?
Date: Tue, 8 Aug 2000
From: "Alan NAYLOR" alan.naylor@skynet.be
Subject: Re: [CONTAX] 120/220 film flatness
Date: Tue, 08 Aug 2000
From: Bob Shell bob@bobshell.com
Subject: Re: [Rollei] 120/220 film flatness
> From: Edward Meyers aghalide@panix.com
> Reply-To: rollei@mejac.palo-alto.ca.us
> Date: Mon, 7 Aug 2000
> To: rollei@mejac.palo-alto.ca.us
> Subject: Re: [Rollei] 120/220 film flatness
>
> Bob, they mention going around the rollers. Does this mean
> Zeiss is testing with magazines like the hasselblad one?
> Some cameras which don't use Zeiss lenses don't bend the
> film before exposure, if my memory is good. Ed
Date: Tue, 8 Aug 2000
From: Edward Meyers aghalide@panix.com
Subject: Re: [Rollei] 120/220 film flatness
Date: Tue, 08 Aug 2000
From: Bob Shell bob@bobshell.com
Subject: Re: [CONTAX] Contax or Hasselblad?
> From: John Coan jcoan@alumni.duke.edu
> Reply-To: contax@photo.cis.to
> Date: Tue, 08 Aug 2000 03:42:41 -0400
> To: contax@photo.cis.to
> Subject: Re: [CONTAX] Contax or Hasselblad?
>
> because I like to have a camera I can leave loaded
> (film flatness issues aside) and pick up for a shot or two
Date: Tue, 15 Aug 2000
From: "Erwin Puts" imxputs@knoware.nl
Subject: [Leica] Several topics
Newsgroups: rec.photo.equipment.medium-format
Date: 18 Aug 2000
Subject: Re: Prints from 6x7 vs. 4x5
>From: Howard Lester hlester@as.arizona.edu
>
> I suppose
>if Robert Glenn Ketchum can make a fine career shooting landscapes
>with a 6x7.. so can I. (But I bet my 4x5's are a lot better!) ;^)
Date: Thu, 24 Aug 2000
From: Bill800si@aol.com
Subject: Report on Focusing.
Date: Mon, 28 Aug 2000
From: calciua@hn.va.nec.com
Subject: [Rollei] Flat glass option on cameras
Date: Mon, 28 Aug 2000
From: calciua@hn.va.nec.com
Subject: Re: [Rollei] Flat glass option on cameras
Date: Tue, 29 Aug 2000
From: calciua@hn.va.nec.com
Subject: Re: [Rollei] Flat glass option on cameras
Date: Tue, 29 Aug 2000
From: Richard Knoppow dickburk@ix.netcom.com
Subject: Re: [Rollei] Flat glass option on cameras
>In all fairness, I do not think the glass insert is a great invention. It
>certainly does bring a benefit when doing macro work, keeping the film from
>buckling, but for everyday shooting, it is a pain in the royal behind. It
>needs constant cleaning, it may at times mar the film and it does mess up
>highlights by creating a strange halo-like effect around them.
>
>Andrei D. Calciu (VA-4270)
>NEC America, Inc.
>14040 Park Center Dr.
>Herndon, VA 20171-3227
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
Date: Thu, 31 Aug 2000
From: ralph fuerbringer rof@mac.com
To: Robert Monaghan rmonagha@post.cis.smu.edu
Subject: glass
From: Frank Loeffel frankloeffel@my-deja.com>
Newsgroups: rec.photo.equipment.large-format
Subject: film flatness problem with Horseman 6x9 cassette for 220
From: Brian Walsh m_che@dcn.davis.ca.us
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: 120/220?? New to MF
Date: Wed, 11 Oct 2000
From: "John M. Niemann" jniemann@ivy.tec.in.us
Subject: Re: [Rollei] loading the L-word
> Jan,
>
> Having loaded an M6 and lost the roll after a nice day out, I learned the
> hard way that loading it is tricky.
> I hate the way it loads, its like something from the stone age. No other
> camera on the market does it this way. Why? Becuase they (L....) don't
> really care. Its far easier to load my TLR.
> As to Canon, well, to each their own. I like a lightweight 35mm SLR.
> Having toted metal SLRs around the world, my shoulder feels much better with
> less weight and I find no problem with the plastic/metal hybrid bodies. Its
> also exceptionally easy to load film in.
>
> Peter K
Date: Thu, 19 Oct 2000
From: Fred Greenspan greenspan@earthlink.net
Subject: Re: [Rollei]Maxwell Screens - Focusing - More than you want to
know!
Date: Fri, 13 Oct 2000
From: bigler@ens2m.fr
Subject: Re: [Rollei] [Fwd: using 61/2x9cm sheet film and glass plates
> Do you know what thickness these glass plates are? Is there a source
> for them? You could use them to make Ambrotypes.
Emmanuel BIGLER
bigler@ens2m.fr
Date: Wed, 18 Oct 2000
From: Fred Greenspan greenspan@earthlink.net
Subject: Re: [Rollei]Maxwell Screens - Focusing - More than you want to
know!
> Marc, Nathan, Toby & etal,
>
> Thanks for the responses. Iam now a bit enlightened with these bright
> screens !
>
> Another followup question..
>
> On my 2.8F (with A bright screen), I focus as sharp as I can, but the
> transparencies/prints are slightly out-of-focus. I noticed this happens
> ONLY if the subject is 10+ feet away. If the subject is close ~ 3 feet,
> the pictures are razor sharp.
>
> The problem could be, the image looks focused on the focusing screen BUT
> not on the film plane. But this should happen for subjects at any distance,
> right ??
>
> I remember there was some discussions on adjustments of these focusing
> screens at the time of installation. When you send the camera to Fleenor or
> Maxwell, they charge for the installation - due to the precise adjustment
> needed. Could it be, I need this adjustment done on my 2.8F ??
> Thanks,
> -Jay
From: vilntfluid@aol.com (VILNTFLUID)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: film flatness problem with Horseman 6x9 cassette for 220
From: Frank Loeffel frankloeffel@my-deja.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: film flatness problem with Horseman 6x9 cassette for 220
> This problem with Horseman RF holders is disconcerting.
> Horseman stuff is not inexpensive and my; understanding
> is that they OEM the Arca backs.
> My suggestion is that you consider discussing this with the
> Horseman distributor and see what their tolerances really
> are. Challenge them to "spec up" your RF holder. I bet you
> could post some "nice" attention getting messages on the
> appropriate message boards that could stimulate their interest
> should they initially demur. We could make one hell of a
> racket (God bless the internet). They or possibly you could
> publish or post those tolerances on the boards and all of us
> could hold their feet to the fire.
> My guess is that 120 backs are not as bad, but this is just
> anecdotal.
> You may just need to load your back and wait the 10 or 20
> minutes for the film to "relax"( in the interim).
> Let me (us) know how you do and if I (we) can help
> you by amassing the hundreds of millions of LF users
> to give support.
Date: Tue, 24 Oct 2000
From: "Kotsinadelis, Peter (Peter)" peterk@avaya.com
Subject: [Rollei] Film Flatness
Date: Tue, 24 Oct 2000
From: Richard Knoppow dickburk@ix.netcom.com
Subject: Re: [Rollei] Film Flatness
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
Date: Tue, 24 Oct 2000
From: Marc James Small msmall@roanoke.infi.net
Subject: Re: [Rollei] Film Flatness
>I was wondering if anyone else has heard of anything that relates to these
>findings?
Date: Tue, 31 Oct 2000
From: Shane W Davis swdavis@umich.edu
Subject: Re: Question about real need of a vacuum back...
Date: Tue, 24 Oct 2000
From: Fred Greenspan greenspan@earthlink.net
Subject: Re: [Rollei] Film Flatness
> In the latest issue of Pop Photo they wrote about the new Zeiss film
> flatness testing. Apparently, there is a new device that Zeiss developed to
> check film flatness in cameras. Although Pop did not disclose much, they
> did indicate that the test proved 220 film will sit flatter (2x flatter)
> than 120. They also indicate that many customers complaints about sharpness
> are attributable to film flatness problems in roll film cameras, and more
> especially the length of time film sits in the camera pressed around
> rollers. Most noticeable with photos taken with the lens wide open.
>
> I was wondering if anyone else has heard of anything that relates to these
> findings?
Date: Tue, 24 Oct 2000
From: Tim Ellestad ellestad@mailbag.com
Subject: Re: [Rollei] Film Flatness
From: Jan Böttcher jab@bios.de
To: rollei@mejac.palo-alto.ca.us rollei@mejac.palo-alto.ca.us
Date: Tuesday, October 24, 2000
Subject: Re: [Rollei] Film Flatnes
>Peter,
>if I had to sell vacuum backs and or ceramic pressure plates, I'd probably
>come to the very same scientific results! In my experience most lack of
>sharpness is a result of improper focusing, second the thought I could hold
>the 200mm lens steady for 1/4th of a second and some time later misaligned
>cameras and poor film flatness is to blame.
>Jan
ellestad@mailbag.com
Date: Wed, 1 Nov 2000
From: "Cousineau , Bernard" bcousineau@tmisolutions.com
Subject: RE: Question about real need of a vacuum back...
> From: Michael R. Hinkle [mailto:lists@mrhphoto.com]
> Not to belabor the issue, but is Contax the only manufacturer to address the
> issue, or have other medium format manufacturers released similar products
> to the vacuum back? My next question is how heavily should I weight this
> functionality Contax offers in my quest for a medium format system.
Date: Wed, 01 Nov 2000
From: Ragnar Hansen raghans@powertech.no
Subject: Re: Question about real need of a vacuum back...
sci.astro.amateur
From: Li0N_iN_0iL@NoSpam.Com (Li0N_iN_0iL)
[1] Re: Ultra Flat Paint or Flocking Paper
>I have looked into Protostar flocking paper, but it seems rather
>expensive. Is it really worth it? Will I get just as good of a result
>with ultra flat black paint? Are there other alternatives or materials
>that I can use or purchase locally?
From: mgw@Astronomy-Mall.com (Mark Wagner)
[Date: Thu Nov 02 2000
1] Re: Ultra Flat Paint or Flocking Paper
: When my wife told me that she was going to buy some brushed
: felt for her sewing and crafts, I had her buy some extra for
: my 'scope. It cost $1.50 a yard (one-twelfth the price of
: Protostar) and seems a lot blacker than paint.
Astronomy-Mall: http://Astronomy-Mall.com
From: Axel riteshlaud@my-deja.com
Date: Wed Nov 01 2000
[1] Re: Ultra Flat Paint or Flocking Paper
> I'm interested in the Protostar flocking paper as well ... where can I
> purchase it?
>
> -- Paul Manoian
From: "Michael R. Hinkle" mrhinkle@mrhphoto.com
Subject: Question about real need of a vacuum back...
Michael
www.mrhphoto.com
Date: Tue, 31 Oct 2000
From: "Q.G. de Bakker" qnu@worldonline.nl
To: hasselblad@kelvin.net
Subject: Re: Question about real need of a vacuum back...
Date: Thu, 2 Nov 2000
From: Roger contaxaholic@yahoo.com
Subject: Re: Question about real need of a vacuum back...
Date: Mon, 20 Nov 2000
From: OWL@uk.ibm.com
To: Robert Monaghan rmonagha@post.cis.smu.edu
Subject: Film Flatness
Then click on
Products
Camera and Cine Lenses
News
Camera Lens News -- Archives
Camera Lens News No. 10
Is rollfilm 220 better than 120 in terms of film flatness?
Senior Internet Security Consultant, IBM Global Services
owl@uk.ibm.com http://www.ibm.com/security/services/
Date: Wed, 15 Nov 2000
From: Richard Urmonas rurmonas@ieee.org
Subject: Re: Medium Format Film Flatness or Not
> No doubt, Zeiss which supplies some of the best medium format lenses made
> today, and to Hasselblad, Rollei and
> Contax, is having the same problem that Nikon had when they supplied fine
> lenses to early Bronica cameras.
> The lenses may be excellent and test well in the lab, but when used on the
> cameras, due to film un-flatness,
> do not deliver the sharp photos they should be capable of, especially at
> wide apertures.
> Why not put the blame where it is deserved - with the film. 120 film is now
> over 100 years old and was originally designed
> as a snapshot film for low quality amateur cameras. Today's high quality
> medium format cameras require film
> designed with the same precision that today's cameras and lenses are
> designed with. It is time for Kodak and the
> other film companies to take this problem seriously and redesign their 120
> and 220 film.
> Note- In a world where we are told that film is losing out and digital
> imaging is in - read the following:
rurmonas@ieee.org
Date: Sat, 02 Dec 2000
From: Javier Perez summarex@yahoo.com
Subject: [Rollei] Curved film planes?????
Date: Mon, 04 Dec 2000
From: Hans-Peter.Lammerich@t-online.de
Subject: Re: [Rollei] Curved film planes?????
Date: Mon, 18 Dec 2000
From: RICH leicaman@email.msn.com
Subject: TechPan
Date: Thu, 4 Jan 2001
From: RICH leicaman@email.msn.com
Subject: RE: hasselblad V1 #1096
Date: Thu, 11 Jan 2001
From: "Austin Franklin" austin@darkroom.com
Subject: [CONTAX] RTS III vacuum back...
Tri-X 0.135mm
Delta 100 0.135mm
160NC 0.150mm
Supra 100 0.150mm
Plus-X 0.150mm
From: "Wayne D" wdewitt@snip.net
Newsgroups: rec.photo.equipment.large-format
Subject: Re: LF lens on MF cameras (specifically Mamiya SLR)
Wayne
Date: Sun, 07 Jan 2001
From: Richard Knoppow dickburk@ix.netcom.com
Subject: Re: [Rollei] testing focus by projection?
>The best resolution for lens-film spacing? That went right over my
>head. What exactly does that mean? As far as I know there is no way to
>adjust the focus of the taking lens - it is solidly mounted to the lens
>board. I suppose you could shim it out, but what would be the point? My
>understanding of coincidence adjustment was that you basically adjust the
>viewing lens to see the same as the taking lens does. Did I miss the boat
>here?
>
>I check focus with a small 20X jewellers loupe. These are quite good
>quality, I got a 4 lens made in germany item (probably from china) for $40
>at a jewelers supply store. They are excellent for checking focus and fine
>detail on a slide, but definitely do not replace a standard loupe. The one
>I have is about the size of my fingernail, so you definitely won't spend a
>lot of time examining medium format slides with them! They also need to be
>very close to focus correctly.
>
>Shaun
>South Korea
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
Date: Thu, 18 Jan 2001
From: Tom Christiansen tomchr@ee.washington.edu
Subject: [CONTAX] Film thicknesses (Was: vacuum back)
>I might also suggest a 'bulletin' or new FAQ item on the Contax web site
>that lists film thicknesses...so we would know what films are 'optimal' to
>use in the RTS III.
Fuji NPH: 122um
Fuji Sensia II 400: 127um
Fuji Provia 100F [RDP III]: 127um
Fuji Velvia RVP: 127um
Date: Thu, 18 Jan 2001
From: "Paul van Walree" odobenus@xs4all.nl
[update: Paul van Walree info@vanWalree.com http://www.vanWalree.com/]
Subject: Re: [CONTAX] FW: vacuum back
> That brings up the issue that I brought up in the first place, which
> is...different film thicknesses. Now that you agree different film
> thicknesses are not compensated for by the RTS III, and it appears the
> camera is calibrated for E-6 0.1524mm...what is the degradation that can
> occur with film that is NOT 0.1524mm in thickness?
Date: Thu, 18 Jan 2001
From: "Austin Franklin" austin@darkroom.com
Subject: RE: [CONTAX] FW: vacuum back
Date: Wed, 17 Jan 2001
From: Raul Lithgo raul_lithgo@yahoo.com
Subject: Re: [NIKON] Why do people buy fast lenses????
Date: Wed, 07 Feb 2001
From: Richard Knoppow dickburk@ix.netcom.com
Subject: RE: [Rollei] Testing focus
>Richard,
>
>If you use a ground glass with tape to the edge you do not account for film
>never being perfectly flat.
>I use the tape on the inside only up to the edges of the opening for the
>film so it protrudes in the thousandths to account for the reality of film
>in a camera. This works better than assuming film is perfectly flat all the
>time (which it is not) as you would if you did it your way.
>
>Peter K
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
From: "Kotsinadelis, Peter (Peter)" peterk@avaya.com
Subject: RE: [Rollei] Testing focus
Newsgroups: rec.photo.equipment.medium-format
Date: 07 Feb 2001
Subject: Re: Hassy Loading..?
Date: Wed, 07 Feb 2001
From: jerryleh@pacbell.net
Subject: Re: [Rollei] Testing focus
Date: Wed, 07 Feb 2001
From: Richard Knoppow dickburk@ix.netcom.com
Subject: Re: [Rollei] Testing focus
>I had Bill Maxwell go over my Rollei 2.8F a while ago, and in the course of the
>process he told me, at great length (he's like that, you know) that focus is set
>some distance ahead of the plane of the film rails to account for the normal
>shape the film takes in the gate. He tried to describe some fiendish device
>that was used to check focus in this way, but I'm afraid I didn't understand much
>of it. I do remember, though, that focus was NOT set at the plane of the film
>rails.
>Perhaps Bob Shell can confirm or deny, from his repair days, that this was normal
>procedure for setting Rollei TLR focus?
>
>Cheers,
>Kip
>
>Richard Knoppow wrote, in part:
>
>> It would be interesting to know just how
>> far from flat film is in a Rollei gate and how its immediate history
>> (whether its just been wound or has sat there for a time) affects the
>> flatness.
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
Date: Thu, 8 Feb 2001
From: Richard Urmonas rurmonas@senet.com.au
Subject: RE: [Rollei] Testing focus
> I thought of this too but I am not sure just what the film does in the
> gate. An auto collimator would be able to dermine exact focus because you
> could see the image on the film. It would be interesting to know just how
> far from flat film is in a Rollei gate and how its immediate history
> (whether its just been wound or has sat there for a time) affects the
> flatness.
rurmonas@ieee.org
Date: Thu, 8 Feb 2001
From: Richard Urmonas rurmonas@senet.com.au
Subject: Re: [Rollei] Testing focus
> I was under the impression (from a few glass-plate discussions on the list)
> that the difference in focus between film flattened with a glass plate and
> film not flattened was pretty neglible.
Date: Thu, 08 Feb 2001
From: Richard Knoppow dickburk@ix.netcom.com
Subject: Re: [Rollei] Testing focus
>> I was under the impression (from a few glass-plate discussions on the list)
>> that the difference in focus between film flattened with a glass plate and
>> film not flattened was pretty neglible.
>
>On the Tele-Rollei I can see the change in focus between the glass being fitted
>and not fitted. The difference is small (well within normal focus tollerance).
> I personally find the glass plate adds a "halation" type of effect and prefer
>not to use it for this reason.
>
>Richard.
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
Date: Sun, 11 Feb 2001
From: Robert Monaghan rmonagha@post.smu.edu
Subject: re: messraster hyperaccurate focusing; auto 3X autofocus
bracketing
Date: Thu, 23 Nov 2000
From: "Mark B. Anstendig" mba@anstendig.com
To: Robert Monaghan rmonagha@post.cis.smu.edu
Subject: Re: query about Messraster
>Greetings,
>
>Enjoyed reading your photography papers re: Messraster, added links to my
>site and autofocus problems pages etc. e.g., see links at
>http://www.smu.edu/~rmonagha/third/af.html AF Problems Pages...
>
>Do you have a source for Messraster screens for any camera? You mention
>in your article(s) that such screens have been made and mounted in
>various cameras, and that such screen production is now readily possible.
>Has anyone followed up since the 1985 article dates with making them
>available? A number of folks make custom screens (Beattie..) and would
>seem to be possible outlets for such custom installed Messraster screens?
>I am not completely clear on the technology of the screen itself. I am
>assuming that it is a surface with many parallel thin lines of alternate
>depth. The alternative interpretation of only two surfaces with a split
>screen would seem to be too simple and easy to build (e.g., just grind
>down one half of a screen a few microns more)
> Other issues like optimal
>size of ground glass grain structure would also be an obvious issue. Can
>you supply further references, e.g., to any US patents or published
>articles or resources which might provide a way to acquire or build such
>a Messraster screen for testing?
Newsgroups: rec.photo.equipment.medium-format
Date: 06 Feb 2001
Subject: Re: Hassy Loading..?
From Rollei Mailing List:
Date: Tue, 23 Jan 2001
From: Edward Meyers aghalide@panix.com
To: "'rollei@mejac.palo-alto.ca.us'" rollei@mejac.palo-alto.ca.us
Subject: RE: [Rollei] What is it with the 25mm Focal length
Newsgroups: rec.photo.equipment.large-format
Date: Wed, 29 Nov 2000
Subject: Re: A tale of ground glass alignment
>My particular fuss has been with film holders. Unless one spends a
>bundle on a vacuum-backed holder, there's so much bowing in 4x5 that
>a Mamiya RB image will be technically better in may respects.
>(like consistency in DOF -- and it doesn't take much looseness to
>produce a noticable difference)...
Date: Mon, 19 Feb 2001
From: qdb@barleigh.com
Subject: [medium-format] Film Flatness & image sharpness
Quentin
Date: Wed, 21 Feb 2001
From: flexaret@sprynet.com
Subject: Re: Re: Film Flatness & image sharpness
Date: Wed, 21 Feb 2001
From: pkkollas@gorge.net
Subject: Re: [Rollei] Rollei Users list digest V9 #62
>> From: Alan Magayne-Roshak
>> I have used my father's Voigtlaeder Bergheil with a Suydam roll adapter
>> that allows either 6x6 or 6x9 format. It's fun to use every so often, but
>> the results are not as sharp as with a modern camera, although pretty
>> satisfying at f/22. I think the film bulges in the adapter,
>
> I think that's the reason too. The Skopar and Heliar are very sharp and
> should at least give results like the Rolleiflexes of that age.
>
> /Patric
Date: 22 Feb 2001
From: keller.schaefer@t-online.de
Subject: Re: [Rollei] focus shift
>this shifts the position of the image by ~1/3 of the plate thickness
>and introduces various losses of image quality. But nobody cares if
>it is for a Polaroid back on a 6x6 SLR.
>
>Emmanuel BIGLER
>
Date: 23 Feb 2001
From: keller.schaefer@t-online.de
Subject: [Rollei] R-TLR plane glass focus shift
>From: bigler@ens2m.fr
> I do not want to start another controversial thread, but it
> seems that the drawbacks in terms of additional flare and the burden
>
> of keeping this glass spotless clean actually resulted *at least* in
> mixed feelings among R-TLR users in the 1960's ; the company
> discontinued the item on the last R-TLR series.
Date: Fri, 16 Mar 2001
From: S Dimitrov sld@earthlink.net
Subject: Re: [Rollei] 6008 film flatness
Newsgroups: rec.photo.equipment.medium-format
Date: 01 Mar 2001
Subject: Re: General guidance on Rolleiflex
Date: Wed, 11 Apr 2001
From: "Q.G. de Bakker" qnu@worldonline.nl
Subject: Re: Film flatness
> Sheet film has a great deal of problems with flatness and with the film
> simply staying in the film plane.
Date: Tue, 10 Apr 2001
From: Robert Meier robertmeier@usjet.net
Subject: Re: Film flatness
> There are very fine sheet film holders that overcome these problems, like
> the Sinar precision sheet film holder cat.no. 566.36, maximum deviation from
> flatness: +/- 0.03 mm, or 1/800".
Date: Wed, 11 Apr 2001
From: "Q.G. de Bakker" qnu@worldonline.nl
Subject: Re: Film flatness
> Yes, that's true. But with a standard 4x5 holder, a Lisco, for example,
> the film can wander around a lot.
Date: Tue, 10 Apr 2001
From: Mark Rabiner mark@rabiner.cncoffice.com
Subject: [Fwd: Film flatness]
Date: Mon, 09 Apr 2001
From: Peter Janke Muecke-Janke@t-online.de
Subject: Film flatness
Date: Mon, 09 Apr 2001
From: Jim Brick jim_brick@agilent.com
Subject: Re: Film flatness
From Rollei Mailing LIst;
Date: Wed, 11 Apr 2001
From: bigler@ens2m.fr
Subject: Re: [Rollei] Re:Using the sheet film back
> I've got some sheet film holders for my Rollei (twinlens), but I am
> apparantly missing a key piece -- I can cut 4x5 film in half, in the dark,
> and load it into the holder, but a backing piece is needed to slide in with
> the film, behind it, to keep it flat. What can I use for this?
RUG list, Tue Mar 7 2000
> >From Guido Cova :
> >I would like to know the exact thickness of this metal plate, as I use a
> >cardboard sheet to compensate for the different thickness (and, obviously,
> >it is far from being flat).
>
> Measured on my kit :
> Plate dimensions : 63.5mm (=2"1/2) by 88.5mm (~3"1/2)
>
> Plate thickness : a little less than 1mm. As far as I have measured at
> home with a 1/20th mm caliper, the thickness would be closer to 0.95mm(!)
>
> But I think the exact thickness is less important than the flatness,
> since some springs push the plate + film towards the focal plane/film
> gate. The more difficult to home-build one of those plates, besides
> flatness issues, might be to find a high quality matte paint for
> finishing. As far as I remember there are some pointers to such kind
> of paint in the RUG list archive.
> >From Mark Blackman :
> >....where I could get one of ....film adaptor ( missing)
>
> Now as far as the choice of the material is concerned I think a 1mm
> thick plate made either of duraluminium (which could be black
> anodised), brass, or steel would do the job. Brass is probably the
> most pleasant to machine by hand. I myself would roughly cut the plate
> with a "bocfil" jeweller's saw, and then grind the edges on a flat
> surface (ideally : one of those perfectly plane heavy cast iron plates
> used in mechanics workshops) with corundum paper to achieve nice
> straight (but non-sharp) edges.
Additional info :
- EFKE 100 B&W (from www.fotoimpex.de)
bigler@ens2m.fr
Date: Wed, 11 Apr 2001
From: Peter Janke Muecke-Janke@t-online.de
Subject: Re: Film flatness
> Peter,
>
> For your type of photography you may want to try a large format camera.
> This system uses sheet film which is quite flat unlike roll film that curls.
> Each sheet is feed into a film holder and each holder has rails called
> rebates. This may be solve your problem. And a plus, sheet film is a
> larger negative (4x5). But, I do love using my Hassy.
>
> Regards,
>
> Frank
Date: Tue, 22 May 2001
From: Jeffrey Muehl jrmuehl@wi.rr.com
Subject: How Long Can Film Remain in Mag. Before Flatness Problems
Date: Tue, 22 May 2001
From: "Q.G. de Bakker" qnu@worldonline.nl
Subject: Re: How Long Can Film Remain in Mag. Before Flatness Problems
> The film was sitting in the mag for about five days. Is it a good idea to
> skip a frame once the film has been siting in the mag for awhile?
> How long is a while?
Date: Tue, 22 May 2001
From: todd todd_belcher@telus.net
Subject: Re: [Rollei] rolleiflex question?
> If the glass is flat, why does the back have a 'hump'? As a note, this
> isn't shown in the Rollei 75 year history book that I could find...
>
> >
> > This is the back for the optical flat glass. John K
Date: Wed, 23 May 2001
From: Austin Franklin darkroom@ix.netcom.com
Subject: RE: FAQ?: 120 vs. 220 tradeoffs
> > What are the tradeoffs involved in shooting 120 vs. 220 film, besides
> > obvious things such as per-roll costs and the convenience of
> being able to
> > shoot more frames between changing rolls?
>
> (specifically with regard to A12 vs. A24 backs)
From Contax Mailing List;
Date: Thu, 05 Jul 2001
From: Randolph Boverman rboverman@earthlink.net
Subject: [CONTAX] Contax 645 sharpness
Fashion Photographer
Meier & Frank
Portland, Oregon
ate: Wed, 11 Jul 2001
From: Erwin Puts imxputs@ision.nl
Subject: Newsletter #13
From: Richard Knoppow dickburk@ix.netcom.com
To: rmonagha@post.cis.smu.edu
Subject: Re: curved film plane w.a. camera? Re: How ..Build A Center
..Filter?
>Has anyone built a camera in which the film is curved to offset the cos^4
>losses (and perhaps problems with flat field results with very wide angles
>of coverage) and thereby avoid center filter requirements at all?
>
>we used to use curved film plates to compensate for various problems on
>our 60 inch telescope, so I wonder if a curved film plane camera is
>feasible and perhaps improve coverage and light losses effects?
>--
>* Robert Monaghan POB752182 Dallas Tx 75275-2182 rmonagha@mail.smu.edu
Richard Knoppow
Los Angeles, Ca.
dickburk@ix.netcom.com
From: HypoBob hypobob@pacbell.net
Newsgroups: rec.photo.equipment.large-format
Subject: Re: curved film plane w.a. camera? Re: How ..Build A Center
..Filter?
San Jose
> Has anyone built a camera in which the film is curved to offset the cos^4
> losses (and perhaps problems with flat field results with very wide angles
> of coverage) and thereby avoid center filter requirements at all?
>
> we used to use curved film plates to compensate for various problems on
> our 60 inch telescope, so I wonder if a curved film plane camera is
> feasible and perhaps improve coverage and light losses effects?
From: Paul and Paula Butzi butzi@nwlink.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: curved film plane w.a. camera? Re: How ..Build A Center
..Filter?
>Yes, but isn't that an effort to essentially flatten the plane
>relative to the lens?
From: "Larry Whatley" linda_aw@ix.netcom
Newsgroups: rec.photo.equipment.large-format
Subject: Re: curved film plane w.a. camera? Re: How ..Build A Center
..Filter?
Newsgroups: rec.photo.equipment.medium-format
Date: 12 Jul 2001
Subject: Re: Pentax 6711
>The biggest drawback in my opinion is the lack of interchangeable backs so
>shooting multiple film types at the same time is a hassle. On the other hand
>the large back keeps the film flatter than any other 6x7.
Date: Fri, 3 Aug 2001
From: "kyounts" ojingoh@sitespecific.net
Subject: Subject: RE: [Leica] Leica Quality versus Medium Format
From: "George Day" george@rdcinteractive.com
Subject: RE: [Leica] Leica Quality versus Medium Format
From: "kab" koshaugh@teleport-spam.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Mamiya TLR question.
> Hello All,
>
> I recently purchased a used Mamiya 330 with 80mm lens. This is
> my first medium format.
> I shoot one roll and the results are somewhat puzzling.
> All four corners seem stretched a little, it is hard to see if there is
> a reduced image quality since it is the corner. Also one of the
> negative sides, shows a jaggy edge along about half of its length,
> when viewed with and x8 loupe.
> Though, both of these can be easily cropped away, I wonder whether an
> experienced user will consider these as serious defect.
>
> Thank you.
>
> MR
From: "John Bateson" j.g.bateson@worldnet.att.net
Newsgroups: rec.photo.equipment.35mm,rec.photo.equipment.large-format
Subject: Re: Superfast lenses; Was: Stanley Kubrick's f0.7 lens
> Would a lens that comes to a focus at the surface of the rear element
> work if film is simply pressed into intimate contact with the glass.
> wrote Nicholas O. Lindan.
John Bateson
From: Bob Mathison support@antiquetools.com
Newsgroups: rec.photo.equipment.35mm,rec.photo.equipment.large-format
Subject: Re: Superfast lenses; Was: Stanley Kubrick's f0.7 lens
From: mike.rott@tuebingen.mpg.de (Mike Rott)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Contax 645 vs Mamiya 645 AF: Take #2
From: "Mike" mfeldman@qwest.net
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Pentax 67II vs. 645
> You want a flat film plane and you will
> be shooting at infinity, . . . so why the SLR?
From: bg174@FreeNet.Carleton.CA (Michael Gudzinowicz)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Film buckle/bulge again
>I wonder if two kind people with a 6x6 and 6x9 camera that they know
>focuses truly and accurately at infinity from the photos they have taken
>with it, and a piece of ground glass could tell me, on the basis of the
>ground glass exactly in the film plane, what REAL distance corresponds
>to the lens set at infinity. This will need to be done with the aperture
>wide open and is probably best done looking at the images of street
>lamps. I'm guessing the 6x6 will focus at 60 feet and the 6x9 at 40
>feet. But that is just a guess.
>
>The reason for this difference is the bulge/buckle of the film towards
>the lens. It is more pronounced with a 6x9.
>
>I know it's not the right group but the Contax RTS III 35mm format
>camera actually sucks the film back against the pressure plate when it
>takes the photo. No kidding. And this is to overcome 35mm film
>buckle/bulge which is much less than for medium format.
From: "Brian Swale" bj@caverock.net.nz>
To: Robert Monaghan rmonagha@post.cis.smu.edu>
Date: Tue, 2 Oct 2001
Hi Robert
The link on your film flatness pages relating to
Motor Drive Second Shot Blur Problem (Grumpy's site)
appears to be dead.
Google caches their searches but it has been dead so long they no longer
have it cached.
Some things are falling into place.
I have now got a Graflex body from Igor's shop in Cleveland, and a Schneider
47mm S/A from Photoinvest in Copenhagen. My goal here includes getting
a Pac Pro setup from Bob Hutchinson.
http://paq.net/paqpro/
However, I now have to make some money to compensate for my recent
buying spree.
Cheers, Brian Swale
Brian Swale
e-mail bj@caverock.net.nz
http://www.caverock.net.nz/~bj/
From: ramarren@bayarea.net (Godfrey DiGiorgi)
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Leica-Konica incompatibility?
Date: Fri, 12 Oct 2001
Discussions of coefficients of expansion and such are red herrings.
Engineers designing and building cameras know their materials and how to
construct high precision devices.
Modern motor vehicle engines today are frequently manufactured with many
tolerances in the sub-.001" range. Cameras and mechanical watches require
higher precision tolerances than that. Read "Camera Technology - The Dark
Side of the Lens" by Norman Goldberg. There are a lot of details to the
discussion of focus tolerances, back focus and film flatness.
Godfrey
ChrisQ lightwork@aerosys.co.uk> wrote:
> Godfrey DiGiorgi wrote:
>
> >
> > Tolerances for back focus and film plane alignment are usually in the +/-
> > .0005-.001" range (to account for film curvature) even on relatively
> > inexpensive cameras.
> >
>
> Need to be convinced. Any documentary evidence of that or links ?.
> Even to provide tolerances of +/- 1 thousandth of an inch, (0.001"),
> is difficult in production and would be degraded by the expansion and
> contraction of the material with temperature ....
[snip]
From: mkirwan@nospampacbell.net (Mike)
Newsgroups: rec.photo.equipment.medium-format
Subject: Film Flatness - Snip from Zeiss - Long Post
Date: Wed, 09 Jan 2002
220 film offers 2:1 improvement in film flatness over 120. Research
conducted by Zeisz - Snip from their web site:
Is rollfilm 220 better than 120 in terms of film flatness?
Zeiss has recently developed a new measuring system to evaluate film
flatness in medium format photography.
The new system is based on an computerized microscope that can
automatically scan and focus on multiple points of a film frame in a
medium format camera magazine. The obtained focusing data are recorded
by a computer and evaluated by a propriatory Zeiss software. The
result is a mapping of the film topography with an accuracy of one
millionth of a meter (1 micron), according to the developer of this
system.
The purpose of this new device is to find out how well film magazine
mechanics are designed in today's medium format camera systems, how
precise they position the film and how well they hold it flat. From
these findings Zeiss can draw conclusions about the field flatness
required for medium format lenses and Zeiss can also trace causes for
lack of sharpness in customer's photos. This is particularly
interesting since more than 99% of all customer complaints about
lacking sharpness in their photos can be attributed to misalignments
of critical components in camera, viewfinder, or magazine, focus
errors, camera shake and vibrations, film curvature, and other
reasons.
So far, Zeiss has found that film curvature can have a major influence
as a source of unsharpness. This has also been known by Zeiss' camera
making partners Alpa, Hasselblad, Kyocera (Contax) and Rollei. Since
Zeiss' evaluation program is not completed yet, we would like not to
draw too many conclusions prematurely. But two things can be stated
already as hints to enable sharper photos with medium format cameras
at wide open apertures, since exactly those are invited by the high
level of aberration correction in Zeiss lenses:
1.
220 type rollfilm usually offers better flatness than 120 type by a
factor of almost 2. This is an advantage with fast, motorized cameras
like the Contax 645 AF, Hasselblad 555 ELD (and previous motorized
Hasselblad cameras) and Rolleiflex 6000 series cameras.
2.
Film flatness problems are mainly caused by the combined influence of
two factors: the rollers in the camera or magazine that bend the film,
and the time a certain part of the film is bent by such a roller.
Camera manufacturers usually space the rollers in a way that bent
portions of the film will never be positioned near the center of the
image. Therefore only marginal regions of the image should be affected
by sharpness problems due to film flatness errors.
Since the photographer cannot alter the geometry and mechanics of his
camera, he can only influence the other factor: time. A film run
through the camera without much time between exposures should result
in good flatness and hence sharpness. Five minutes between exposures
may be some sort of limit, depending on brand and type of film. 15
minutes are likely to show an influence of bending around rollers. Two
hours definitively will.
As a rule of thumb: For best sharpness in medium format, prefer 220
type roll film and run it through the camera rather quickly.
From: "eMeL" badbatz99@hotmail.com>
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Film flatness on Rollei 6000 series
Date: Sat, 27 Oct 2001
Neurula [Sydney] intelligence@!!!technologist.com> wrote...
> Hi I've learnt from reading posts on photo.net that there are problems of
> film not being flat in the film back resulting in the final image being
out
> of focus, the various posts seem to suggest that this problem is
especially
> prone in Rollei cameras, however they did not say which type of Rollei, I
> suspect that they mean Rollei TLRs? what about rollei 6000 series, has the
> mistake been corrected?
According to Zeiss, one should run a roll of 120 film through the camera as
quickly as possible, without too long pauses between expositions.
Full text in English available at
http://www.zeiss.de/C12567A8003B58B9/allBySubject/134AEE504E89CD50C125696200
39712C
(long link - must be on one line.)
Searching Google for "film flatness" + zeiss returns a lot of interesting
links...
Having said that, I must admitt that I am unable to critically verify any
differences between sharpness offered by 120 and 220 in my Rolleis (6001 and
6008i.)
Michael
From: "Bernie Kubiak" bkubiak@mediaone.net>
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Film flatness on Rollei 6000 series
Date: Sat, 27 Oct 2001
eMel wrote:
> According to Zeiss, one should run a roll of 120 film through the camera as
> quickly as possible, without too long pauses between expositions.
>
This is what Zeiss offers on the topic (quoting from their web site):
"1. 220 type rollfilm usually offers better flatness than 120 type by a
factor of almost 2. This is an advantage with fast, motorized cameras like
the Contax 645 AF, Hasselblad 555 ELD (and previous motorized Hasselblad
cameras) and Rolleiflex 6000 series cameras.
2. Film flatness problems are mainly caused by the combined influence of
two factors: the rollers in the camera or magazine that bend the film, and
the time a certain part of the film is bent by such a roller.
Camera manufacturers usually space the rollers in a way that bent portions
of the film will never be positioned near the center of the image. Therefore
only marginal regions of the image should be affected by sharpness problems
due to film flatness errors.
Since the photographer cannot alter the geometry and mechanics of his
camera, he can only influence the other factor: time. A film run through the
camera without much time between exposures should result in good flatness
and hence sharpness. Five minutes between exposures may be some sort of
limit, depending on brand and type of film. 15 minutes are likely to show an
influence of bending around rollers. Two hours definitively will.
As a rule of thumb: For best sharpness in medium format, prefer 220 type
roll film and run it through the camera rather quickly."
Camera Lens News No. 10, Summer 2000
That said, a huge number of my 120 negs must be "unflat" and unsharp -- its
just that I never noticed!
From: "Roland" roland.rashleigh-berry@virgin.net>
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Film flatness on Rollei 6000 series
Date: Sun, 28 Oct 2001
My Rolleiflex TLR 3.5F feeds between two rollers that detect the thickness
of thr film increasing and then bends through 90 degrees onto the area where
it will be exposed. You have maybe got this mixed up with another TLR.
Certainly my Minolta Autocord pulls the film stright down off the roll and
then bends through 90 degrees after exposure or the Mamiya TLRs do not bend
through 90 degrees at all.
Robert Monaghan rmonagha@smu.edu> wrote..
>
> the Rollei TLRs use a non-bending, straight off the roll film path, so
> they tend to produce very good results as far as flatness issues go.
>
> film flatness is mainly an issue with fast lenses, used wide open, with
> biggest problems observed with rolls of film that have been left sitting
> in the camera for some hours or days.
>
> see http://people.smu.edu/rmonagha/mf/flat.html for more details etc.
>
> HTH bobm
From: nimages@capecod.net (David Grabowski)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Film flatness on Rollei 6000 series
Date: Sun, 28 Oct 2001
"Roland" roland.rashleigh-berry@virgin.net> wrote:
>My Rolleiflex TLR 3.5F feeds between two rollers that detect the thickness
>of thr film increasing and then bends through 90 degrees onto the area where
>it will be exposed. You have maybe got this mixed up with another TLR.
>Certainly my Minolta Autocord pulls the film stright down off the roll and
>then bends through 90 degrees after exposure or the Mamiya TLRs do not bend
>through 90 degrees at all.
Yes and in the case of the Mamiya , they also have strong pressure
plates with decent guides along the films edge. Now the RB backs
really twist the film up, both before and after the taking area with
the film coming off the inside most section of spool and actually
bending backwards past 90 deg. I shoot a lot of 120 , though generally
shot off in half an hour or less per roll, sometimes a roll may be in
for an entire day. Never noticed a problem worth dicussing.
The Rollei TLR while working the film through rollers as another
poster mentioned , still makes a 90 deg. bend. Some of my most
impressive prints are from this camera and that certainly has film in
it for extended periods of time, since I use it for vaction shooting.
In the end, to the original poster, I just wouldn't worry about it !
David Grabowksi
>
>Robert Monaghan rmonagha@smu.edu> wrote...
>>
>> the Rollei TLRs use a non-bending, straight off the roll film path, so
>> they tend to produce very good results as far as flatness issues go.
>>
>> film flatness is mainly an issue with fast lenses, used wide open, with
>> biggest problems observed with rolls of film that have been left sitting
>> in the camera for some hours or days.
>>
>> see http://people.smu.edu/rmonagha/mf/flat.html for more details etc.
>>
>> HTH bobm
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 27 Oct 2001
Subject: Re: Film flatness on Rollei 6000 series
I have been doing an ongoing study of film flatness problems in
120 cameras, by photo tests and examining the cameras.
I recently examined the Rollei 6000 series SLRs with their straight
across film path and good design and my initial reaction is that these cameras
should have some of the flatest film planes in 120 photography today. Not that
any 120 camera is perfect, but with the high quality lenses that come with
these cameras and their great reputation in
Europe - they must be capable of truly sharp results.
Mind you, not that any 120 camera is perfect in that regard, since
120 film (and by extension 220 film) is 100 year old technology which
greatly needs redesigning to a new type of film which will create a
flatter film plane and work in exisitng 120/220 cameras.
Believe it or not some other cameras with very flat film planes include-
Bronica S2A with the later 12/24 back and the later "A" one
roller film insert.
Kiev 88 or Kiev 88CM with the new NT back.
Hasselblad - any model with the newly adapted Hasselblad version of
the Kiev NT back.
All versions of Pentax 67
Pentacon 6 with an optical glass plate installed in the aperture.
Mamiya 6 and Mamiya 7 rangefinder cameras.
Mamiya 6x7 SLR
These are just my opinions - make your own tests and observations.
The flattest film plane is on the Contax 645 with vacuum back
for 220 film only.
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 29 Oct 2001
Subject: Re: Film flatness on Rollei 6000 series
I was speaking about film flatness on 120/220 film.
I am sure the Rollei 70MM vacuum back is a great product.
What it and the Contax 645 vacuum back both are evidence of - is
that the rest of the 120/220 cameras and backs do HAVE film flatness problems
to one degree or another.
So, for critical/scientific sork they had to design the vacuum backs.
Date: Sat, 3 Nov 2001
From: Joe B. joe-b@mozartclara.co.uk>
Subject: Re: Film flatness on Rollei 6000 series
Newsgroups: rec.photo.equipment.medium-format
Neurula [Sydney] wrote
> Hi I've learnt from reading posts on photo.net that there are problems of
> film not being flat in the film back resulting in the final image being out
> of focus, the various posts seem to suggest that this problem is especially
> prone in Rollei cameras, however they did not say which type of Rollei, I
> suspect that they mean Rollei TLRs? what about rollei 6000 series, has the
> mistake been corrected?
I did read somewhere that the 6000 series was designed as a "tall" rather
than "long" (front to back) body for this reason. The 6000 series body is
tall with a tall film back which holds the film rolls above and below the
film gate. The earlier Rollei SL66 (MF SLR predating the 6000 series) has a
long low body with a squat film back holding both rolls behind the film gate
making a bend both before and after exposure. The Rollei TLR is a tall body
but it has a fairly sharp 90 degree bend from underneath before the film
reaches the gate. So the 6000 series should be the best of the various
Rolleis in this regard, if the bends are what matters.
Joe B. [remove composer for email]
From: chinesecameras@yahoogroups.com
Date: Fri, 11 Jan 2002
From: "Per Backman" pbackman@algonet.se>
Subject: Flocking and Seagull TLR
Hello,
A good way to rise contrast of the images is to put black material in the camera. I have the lower part of the very camera (behind the lens and in front of the film, sometimes
I can not find the words in English) covered with black material, and it does rise the contrast pretty much. There is special self-adhesive material for the purpose, and I
think it is really something worth considering.
Per
The PHOTO page;
Images (nude), B/W Formulae (lots of them);
In English, auf deutsch, po polsku;
http://hem.fyristorg.com/pbackman/
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 10 Jan 2002
Subject: Re: Film Flatness - Snip from Zeiss - Long Post
Films Flatness in medium format can me measured if one is dealing with a camera
in which the lens can be removed or a back taken off the camera. (Not easy to
measure on fixed lens Twin Lens Reflexes or
Fixed lens Folding Cameras.
I have been interested in wider aperture macro photography and portrait
photography with 180MM lenses wide open at f2.8, to retain a sharp image and
blurr out the background. These are special uses where
film flatness problems will cause focus problems.
If one is shooting at f8 to f16, any residual lack of film flatness
(unless the camera is horribly off alignment) will usually be eliminated by
depth of focus. However, areas in an image can be sharp which
the photographer would rather have out of focus. It is necessary (with an SLR)
to check the image with the lens stopped down (not all lenses and cameras can
do this) to see in the finder exactly what will be in focus and out of focus.
I have found by testing camera backs with film and SLR cameras with lenses
removed that there is a big variation in film flatness due to
type of camera, back, film and which exposure is on the roll of film.
Based on this study of my own equipment, I only use certain cameras and backs
for critical work as I know the others may have film flatness issues.
When I talk about "film flatness issues" - that is not to imply that an entire
image will be out of focus. A slight ripple in the film can move a
small section of the film forward, putting a relatively small part of the
picture out of focus. We have all seen this phenomenon, but as much of the
picture was in focus we did not give it any attention.
- Sam Sherman
From: Stephe ms_stephe@excite.com>
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Film Flatness - Snip from Zeiss - Long Post
Date: Fri, 11 Jan 2002
FLEXARET2 wrote:
>
> If one is shooting at f8 to f16, any residual lack of film flatness
> (unless the camera is horribly off alignment) will usually be eliminated
> by depth of focus. However, areas in an image can be sharp which
> the photographer would rather have out of focus.
The other thing I've found is that while this depth of focus covers this
"error" what you are seeing is "acceptable" focus, not sharp focus. It does
little good IMHO to have the "worlds best" lens and then have the film
flatness such that you're dealing with acceptable focus covered by DOF.
This is no different than having a focusing screen out of calibration
except you have no idea when and if the focus point will change!
I feel that image quality is everything in the system added together. The
stability of the tripod, the quality of the filters used, the flatness of
the film plane, the resolving power of the lens, the calibration of the
focusing device etc. Small errors in one item isn't going to make a huge
difference i.e. enough to throw away the image, but then again every place
you fudge something is degrading the image to a certain extent that has to
be made up somewhere else.
Point being a camera with good film flatness and an OK lens can make as
good a picture as a camera with a "world class" lens and OK film flatness.
--
Stephe
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 13 Jan 2002
Subject: Re: Film Flatness - Snip from Zeiss - Long Post
Film flatness will vary with each type of camera regardless of
how the film bends - pressure plates, rails, rollers, tension, type of
film all figure into this.
Lots of great sharp photos taken with Rollei TLRs - somehow the
film must be reasonably flat in those cameras. I have never had a problem with
Rollei TLR cameras.
-Sam Sherman
From: Stephe ms_stephe@excite.com>
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Film Flatness - Snip from Zeiss - Long Post
Date: Sun, 13 Jan 2002
Ralf R. Radermacher wrote:
> Stephe ms_stephe@excite.com> wrote:
>
>> I just got a kit from http://www.baierfoto.de/ that includes two pieces
>> of felt like material for each side of the film gate to help increase
>> film flatness even more.
>
> These strips are there to eliminate flare caused by reflection on the
> chrome-plated roller.
>
Actually the instructions say "These parts -exactly as high as the film
rails- will have a positive effect on film flatness, too". Sam said he
checked his before and after and the strips in the baire kit did help..
--
Stephe
From: Stephe ms_stephe@excite.com>
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Film Flatness - Snip from Zeiss - Long Post
Date: Sun, 13 Jan 2002
Q.G. de Bakker wrote:
> Stephe wrote:
>
>> [...] I heard
>> that the newest 'blad backs are using the same technology a K-60 does
>> with a keyed supply spool mount with tension applied to help tension the
>> film across the film gate.
>
> Are they ('blad) still doing that? I thought they had given up on the idea
> and no longer included the "friction brake".
> Such a film surface stabilizer was first used in the early 1950s (Olympus'
> 1951 Chrome Six Model III comes to mind). They work quite well, but only
> as long as there is a rather straight film winding path.
You'd know better than I. I read they started doing this and that it was
causing problems with the winding mechanism so maybe they have stopped?
it does help and this does make a fairly large difference in the results a
camera can produce. As the artical said it can make enough difference where
someone won't see the difference in a older design and the "newest latest
greatest" lens. Until one gets the film flatness under control, is there
much use in getting a "perfect" lens?
--
Stephe
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 13 Jan 2002
Subject: Re: Film Flatness - Snip from Zeiss - Long Post
You would be amazed at how incredibly flat the film plane is on-
1- New Kiev NT backs which fit Kiev 88, Salyut-C and Kiev 88CM cameras.
2- Bronica S2A - 12/24 later model backs with improved "A" - one
top roller film insert.
These two are much flatter than most others I have tested.
The Bronica allows sharp images with adapted 180MM f2.8 Sonnar
wide open at f2.8.
Re- flat film planes - all users should conduct their own tests
with a spare role of 120 or 220 film and looking through the front
of an SLR without lens and shutter open at "B" - you will soon get to realize
what a flat film plane and unflat film plane are.
-Sam Sherman
PS - Re - flocking film plane of Kiev 6C (improved flatness) - flocking of Kiev
60 film plane (reasonable flatness) - with felt strips cut down to 3/8" wide
only. These were not the Baier kit.
From: Gannet gannet@jtel.net>
Newsgroups: rec.photo.equipment.35mm
Subject: Re: A prediction on the decline of 35mm -- circa 1972!
Date: Tue, 15 Jan 2002
Joe Wilensky jjw33@cornell.edu> wrote:
>Any comments? Was the film flatness issue what kept Instamatic film from
>taking its place as the world's preferred format? Was it the
>introduction of autofocus point-and-shoot 35mm cameras in the late '70s?
Heh! Fascinating, thanks for posting that!
Film flatness was never the issue for any but advanced amateurs - and
Kodak pretty much ignores them in their marketing plans. Let's face
it, if you're shooting with a plastic-lens Instamatic permanently set
on f11...what's film flatness? :)
IMO, the real issue, as another poster noted, was that Kodak was
stupid and greedy. As they are today.
Other manufacturers, especially the Japanese, resisted adopting 126
because they didn't want to pay royalties to Kodak. Kodak lost
interest in 126 when the patents expired and they attempted to switch
everyone to 110, and then discfilm, and most lately APS. Each
iteration of this strategy was less successful than the last in terms
of overall market penetration and, perhaps more importantly, staying
power.
This shows a basic difference in business philosophy. Kodak only
really gets excited about something when they can create a monopoly
and milk it. The notion of competing as equals on the basis of
quality and value doesn't enter their minds.
Kodak also has complete contempt for their customers. They think that
quality doesn't matter, that the "average consumer" they target can't
tell the difference between good, mediocre and awful quality. Hence,
whatever Kodak can deliver that is "good enough" and has the lowest
product cost is what they are going to release.
Enough Kodak-ranting, back to the P&S 35 kills 126 issue (which I
think is exactly what happened): this relates back to corporate
culture. Kodak always sees themselves as a film company. They
haven't been a camera company in a long, long time and don't want to
be. The only reason they ever sell cameras at all is to sell film.
As such, Kodak doesn't want to spend R&D money on cameras (yes, there
are exceptions re: digital, etc., but they remain exceptions). Add in
Kodak's "good enough" notions and, heck, Instamatics are "good
enough", right? Camera R&D would be a waste of money.
The Japanese camera companies, OTOH ( with the exception of Fuji and
Konica), are strictly hardware companies. Hardware companies with an
aversion to paying anyone royalties on anything.
Put these two things together and what you get is a situation where
the Japanese camera companies were the only ones funding R&D and
moving cameras into the modern age, and they weren't inclined to do
that on the 126 platform.
The ostensible consumer problem that 126 solved was difficulty with
film loading. And indeed, many 35mm cameras of the 50s and 60s had
film loading that was, um, "awkward". But for Kodak, the -real-
"problem" that 126 solved was to get people locked into Kodak's
revenue stream, either directly through buying Kodak film, or
indirectly through royalties.
But from the camera companies' point of view, it was the former
problem that was of interest. And they solved that, not by
redesigning the film cartridge, but by redesigning the camera. Today,
we usually think of the advent of AE, and later AF, as the hallmarks
of the point & shoot. But I would argue that the crucial innovation
was the "quick loading" (to borrow one companies' term) systems that
made it easy for even Aunt Minnie to load a 35mm camera. From the
consumer's point of view, there went 126's advantage, right out the
window.
Upshot, the only companies that were bringing quality AE and AF to the
table, were also doing this via quick-load 35 cameras. Consumers
wanted the higher quality these cameras offered (note, they were no
EASIER to use than an Instamatic) and moved to them in droves. Kodak
could take a note here. People can and will pay more for better
quality, and they know it when they see it. But you have to show it to
them.
You could argue that this whole episode was the seminal event of the
photo market of the late 20th century. Kodak bet that consumers would
accept mediocre quality as long as it was easy to use and had a low
cost of entry. Japan bet that consumers would pay a lot more for
higher quality as long as it was easy to use. Although the whole
thing is hardly a "decided issue", over time, Kodak has lost share and
Japan has gained it.
>From a corporate culture point of view, Japan tends to figure out how
to do quality first, and then figure out how to do it at a price the
market will bear. They trust that quality will be its own reward in
terms of customer satisfaction and hence sales. Kodak (and American
companies in general) tend to look at what can be produced most
cheaply first, and then figure out how much additional money has to be
put in to get it to a quality level that the consumer (at least those
in focus groups) considers "acceptable". The fallacy in the American
approach is that long-term customer satisfaction is not the same thing
as short-term satisfaction, and it is long-term satisfaction that
drives repeat business. American companies target only the former and
when they lose share over time, they wonder why. People wise up, is
why.
>And ... is there anything we can learn from this today?
Hmmm, not sure. Perhaps that Kodak apparently hasn't learned much? :)
Also, referring back to the book author's statements, that future
market or technological trends that seem "inevitable" are rarely so.
:)
I do think the overall lesson is that you can generate early sales
with low price and convenience, but that over time, people WILL seek
out higher quality, the best that they can find at the price they care
to pay. And hence, that producers who strive to produce the highest
quality for the money spent will tend to prosper over time.
My nickel's worth.
Gannet
St. Petersburg, Florida USA
gannet@jtel.net
From: "Austin Franklin" darkroom@ix.netcom.com>
To: rollei@mejac.palo-alto.ca.us>
Subject: RE: [Rollei] Right back for 220 TLR?
Date: Sun, 2 Dec 2001
> I've not seen it stated for Rollei, but it makes sense. Cameras
> which switch the pressure plate for 120 or 220 do so to compensate
> for the difference in thickness of the two due to the lack of backing
> paper on 220.
>
> Bob
Hi Bob,
I've always been curious about this, and never really spent the time to
investigate it (except for our previous discussion on the vacuum back on the
RTS III).
It's a given that the film, whether 120 or 220 is typically (...except when
using a vacuum system) registered against the front side of the film channel
closest to the lense (typically on some machined rails)...and, at least in
my 120 cameras the pressure plate presses against "stops" that maintain a
fixed distance between the pressure plate and the front rails, making a
"channel" for the film to slide through without any "binding". 35mm does
this same thing.
But...does the 220 setting not use the stops, or have different stops,
therefore changing the film channel size, and without stops, the pressure
plate does in fact press the film against the front rails, causing some
binding? Do some cameras have a second set of stops that are used when the
pressure plate is moved over to the 220 setting?
My Fuji GS645, which is switchable between 120 and 220...has stops for the
120 setting, but none for the 220 setting. That would mean no "extra" space
in the film channel only enough for the film, that the film has constant
pressure on it between the pressure plate and the front rails. This is
unlike 35mm, which maintains free space in the film channel, at least in my
Contax and Leica cameras, and 35mm film doesn't have backing paper either.
My Pentacon TL does support both 120 and 220, but does not have any
different pressure plate setting. Also, on the Hasselblad list, there was a
discussion that the pressure plate and the case etc. are all the same for 12
or 24 backs, the only difference is the advance/counter mechanism...and if
Hasselblad believes there is no need for a difference, I am curious why
others believe there is.
Does anyone have any more information or thoughts on this?
Austin
From: "Austin Franklin" darkroom@ix.netcom.com>
To: rollei@mejac.palo-alto.ca.us>
Subject: RE: [Rollei] Right back for 220 TLR?
Date: Sun, 2 Dec 2001
> Have you ever used a depth micrometer
> to measure the difference in height 'tween
> the 24x36 and the 6x6 position?
Jerry,
What did you find for measurements?
> ...Dork-Riger...
I don't believe this was really necessary, was it?
> but
> the ultimate arbiter is testing.
Most of the time, that is entirely true...testing isn't always done
"correctly" and conclusions correct.
What you said above makes me believe that you, in fact, measured the
difference (or sameness) in the two settings, but that's measuring...not
testing. Have you actually tested 120 vs 220 film for sharpness/flatness in
the Rollei? If so, I, and I am sure, many others, would like it if you
would share the details of your experiment and the resulting data with the
list.
Regards,
Austin
Date: Sun, 2 Dec 2001
From: Sven Keller keller.schaefer@gmx.de>
To: rollei@mejac.palo-alto.ca.us
Subject: Re: [Rollei] Right back for 220 TLR?
David,
yes, we went through this several weeks ago (and it can be re-read in the
FAQ document) but apparently with not much progress.
The 35mm position does NOT move the plate to avoid collision with elements
of the Rolleikin device. Its just the other way round. The plate is designed
such that it inhibits closure of the back when the back is set to the (wrong)
6x6 position with the Rolleikin fitted.
And it DOES reduce the depth of the film channel for 35mm, which is its
ultimate purpose.
You are correct in saying that Rollei recommends the 6x6 position even for
220 film. The SLX and the SL 66 also both have a 220 setting which does not
alter the film channel dimensions.
Apparently the position the 220 film actually takes in the camera is better,
i.e. closer to the optimum film plane with the plate set to 6x6.
Sven Keller
>Dirk,
>We went through this several weeks ago. The 35mm position moves the plate
>to avoid collision with elements of the Rolleikin devices. It does NOT
>reduce the depth of the film channel for 120/220 film.
>The 6x6 position is the correct one for 220 film.
>Best Regards,
>David Seifert
>dseifert@absolute.net
> you wrote:
>>nope, you have to switch into the 35 mm position as the 220 film has the
>>same thickness as the 24x36 film due the missing paper.
>>
>Dirk
--
GMX - Die Kommunikationsplattform im Internet.
http://www.gmx.net
Date: Sun, 02 Dec 2001
To: rollei@mejac.palo-alto.ca.us
From: Richard Knoppow dickburk@ix.netcom.com>
Subject: Re: [Rollei] Right back for 220 TLR?
you wrote:
>Dirk,
>
>We went through this several weeks ago. The 35mm position moves the plate
>to avoid collision with elements of the Rolleikin devices. It does NOT
>reduce the depth of the film channel for 120/220 film.
>
>The 6x6 position is the correct one for 220 film.
>
>
>Best Regards,
>
>David Seifert
>dseifert@absolute.net
>
At the time of that discussion I got curious as to what was actually
going on. I inspected the back plate and made some measurements.
The plate has four little legs on it, at the sides near the corners.
These rest against a surface below the film rails and establish the
clearance of the film channel. On my MX and Rolleicord IV the legs rest
against either a raised area for 120 film, or against the surface of the
film gate, for 35mm. On my 2.8E there is a stepped reference surface, again
moving the back plate towards the lens for 35mm film.
The two versions of the Rolleikin are not quite the same. For the MX and
'cord the film plane is very slightly closer to the lens than it is for
35mm film. On the E it is the same, at least within my ability to measure
it. By memory, the distance is around 1.5X the thickness of the film and
paper, or of the 35mm film alone. I posted the measurements of the film
channel width at the time, must be two or three months ago now, so they
might be in the archives.
I was originally under the impression that the back plate moved only to
clear the Rolleikin arm. In fact, it also does that, but the main reason
for sliding it is the change the clearance for the film.
Evidently, the back plate does NOT press the film against the rails.
I am not quite sure what mechanism is used to locate the film. I did some
checking on other cameras. My Nikon F also has a film channel and its about
the same as the channel with the Rolleikin. Ditto for a Kodak 35 camera.
The main difference between 120 and 35mm is that the 35mm gates have some
edge guidance.
My intuition is that 220 film has some more room to flop around in the
film channel. Its the same thickness as 120 film without the paper, 3.6
mil., according to a Kodak Tri-X data sheet. I haven't tried to calculate
whether this is enough to cause film plane problems.
35mm film is thicker than 120 but not nearly as thick as 120 plus the
paper backing.
BTW, I calculated the depth of focus for the older type Rolleikin and it
appears there should not be a significant defocusing error from the shift
in focal plane. I think I may have posted the numbers for this also.
BTW, I wonder how many people who make lens comparisons on film ever
explore the issue of consistant and repeatable focal plane location plus
errors in focusing methods.
Many years ago Kodak (or maybe it was NBS) published a technical paper
describing a special camera for measuring lens resolution. Kodak
(definitely Kodak) also published a description of a camera used for
measuring film resolution. Very interesting just how complex such a design
can get when all the errors must be controlled and known. Lens or film
performance tests are not easy to make if they are to be reliable.
----
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com
From: Rei Shinozuka shino@ubspw.com>
Subject: Re: [Rollei] Right back for 220 TLR?
To: rollei@mejac.palo-alto.ca.us
Date: Sun, 2 Dec 2001
> From: "Austin Franklin" darkroom@ix.netcom.com>
>
> > You are correct in saying that Rollei recommends the 6x6 position even for
> > 220 film.
>
> Would you mind pointing me to where Rollei mentions this?
austin,
here's from my own files:
it's verbatim even down to the line breaks.
[braces included to explain figures].
-rei
4-page, 6-language insert included in
"Rolleiflex 3.5F/2.8F in practical use"
owner's manual (1968)
---------------------------------------------
Film Transport Mechanism
for No. 120 and 220 film
The lever next to the film counter window
switches the film transport to either 12 ex-
posures (No. 120 roll film) or 24 exposures
(No. 220 roll film).
12 Exposures (No. 120 roll film)
Set the change-over lever to the stop so that
the marking "12" on the knob is upright (1)
[(1) refers to picture 1 showing No. 12 up]
Advance the film in the usual way (see pages
8 to 10 of the instruction book).
24 Exposures (No. 220 roll film)
1. Load the No. 220 roll film in the usual way.
Keep the film pressure plate in the posi-
tion marked "6 x 6".
2. Close the camera back.
3. Now -- and only now, with the film
counter showing No. 0 -- set the change-
over lever to the stop so that the marking
"24" is upright (2)
[(2) referes to picture 2 showing 24 up]
4. Advance the film in the usual way for the
first 12 exposures.
5. After the 12th exposure the crank blocks.
Bring the crank back into the rest position.
Move the change-over lever to bring the
"12" marking upright (1). This returns the film
counter to 0. press the release button (the
shutter does not operate). The crank is
now free to continue advancing the film.
6. Advance the film in the usual way for the
remaining 12 exposures. (The film counter
runs through from No. 1 to No. 12 again).
To check the number of unexposed frames,
subtract the number in the film counter
window from from the upright marking of the
change-over lever.
Resetting the film counter for the second
series of exposures results in a blank frame
in the middle of the film length. This provides
a convenient point for cutting the film in two
later on.
Rollei-Werke
Franke & Heidecke
33 Braunschweig
0270 G & I Printed in Germany
From: Alan Browne alan.browne@videotron.ca>
Newsgroups: rec.photo.equipment.35mm
Subject: Re: film DOfocus etc. Re: Poor Mans Leica ?
Date: Sun, 02 Dec 2001
Neat.
This is aluded to in the book "The Hunt for Red October".
Skunk Works did a lot of camera work as a contractor sending the work out to optics
companies in the US. I saw a very neat (not to mention large!) U-2 camera at the US
War Museaum in Duxford (UK). The mass of film is so high, that to preserve weight
and balance of the aircraft, it had split film running in opposite directions so
that the weight on oposing takeup reels would balance the coaxial "give" spool loss
of film.
Cheers, Thanks for the link.
Alan
Gordon Moat wrote:
>
> Speaking of film flatness, any comments about the Contax vacuum back? And have
> you ever seen this:
>
> http://www.cameraquest.com/nfspy.htm>
>
> Ciao!
Date: Mon, 3 Dec 2001
From: Sven Keller keller.schaefer@gmx.de>
To: rollei@mejac.palo-alto.ca.us
Subject: RE: [Rollei] Right back for 220 TLR?
That I don't know for sure. The film channel in fact has different
dimensions for both plate positions and even with my limited ability
to measure this it is obvious that the film has plenty of room to move.
As Rollei definitely says 'use 6x6 for 220' and as the SLX and the SL 66 are
both designed to take 220 without changing the film channel we obviously
have to say goodbye to the simple thinking of 'take the ideal optical film
plane, add the film thickness and there you have the perfect position for the
pressure plate'.
It seems that the best position for the plate rather is the one that
positions 'the' film closest to the ideal position, despite all its buckling and
bending - alas, a matter of testing and experimenting. If there was less room in
the film channel the film might buckle inwards, instead of staying in the
proper plane.
I ran into this when trying to verify why Rollei specifically advised (in
bold letters!) against the use of SLX backs on 6008 cameras because of film
flatness issues - despite the fact that on all SLX/6000 cameras the film plane
is on the BODY not on the back/magazine. I sacrificed a roll of film and
watched it run through the camera with the lens taken off. I could not really
measure anything but when slightly touching the film I could see it moving, so
wherever it actually was positioned, it was not running flat against the
pressure plate.
Sven Keller
> If it DOES reduce the depth of the film channel for 35mm film, then why
> wouldn't you use it for 220 also, since the film thickness for the same
> film, would be the same in most cases?
>
> > And it DOES reduce the depth of the film channel for 35mm, which is its
> > ultimate purpose.
--
GMX - Die Kommunikationsplattform im Internet.
http://www.gmx.net
Date: Mon, 03 Dec 2001
Subject: Re: [Rollei] Right back for 220 TLR?
From: Bob Shell bob@bobshell.com>
To: rollei@mejac.palo-alto.ca.us>
> From: Robert Monaghan rmonagha@post.cis.smu.edu>
> Date: Sun, 2 Dec 2001)
> To: rollei@mejac.palo-alto.ca.us
> Subject: RE: [Rollei] Right back for 220 TLR?
>
> for those who may have missed them, there were a series of articles in the
> August 1999 British Journal of Photography, a study also reported in
> the Zeiss's Camera Lens News #10 (summer 2000) Is rollfilm 220 better than
> 120 in terms of film flatness? (used to be online but no search engine
> hits now) reporting on zeiss measurements showing 220 was flatter (by a
> factor of two) than 120 in their study. They also recommended shooting
> fast (5 min between shots no problem, but 15 minutes delay shows effects
> of film bending/buckling starting, and full effect in a few hours, so if
> delaying shooting, consider the above if sharpness is critical)...
>
This has long been known, that film tends to acquire a "set" when left too
long between shots. It is a serious concern with film magazines which
introduce a reverse curl into the film, such as Hasselblad, Bronica, Mamiya
645, Contax 645, Fuji 680, etc., and it is much less of a concern with
cameras having a straight film path, such as Rollei SLX & 6000, Fuji GW 670
& 690, Plaubel Makina (the Japanese ones), Graflex XL, Mamiya RB & RZ, and
so on.
As I recall, Zeiss never said what camera system they used in their tests,
but I had the strong impression that they were talking about Hasselblad.
Bob
Subject: AW: [Rollei] Right back for 220 TLR?
Date: Mon, 3 Dec 2001
From: "Sven GMX" keller.schaefer@gmx.de>
To: rollei@mejac.palo-alto.ca.us>
To add to all that has been said I have just taken out a Rolleiflex with
flat glass provision and measured the film channel with the flat glass
fitted. As expected, the film channel in this configuration is very
narrow, something like 0.01 inch - about the same thickness as 120 film
plus backing paper. So in this case there is no surplus space to allow
the film to cup and buckle - the film is positioned just where Carl
Zeiss wants it.
Sven Keller
> At the time of that discussion I got curious as to what was actually
>going on. I inspected the back plate and made some measurements.
> The plate has four little legs on it, at the sides near the corners.
>These rest against a surface below the film rails and establish the
>clearance of the film channel. On my MX and Rolleicord IV the legs rest
>against either a raised area for 120 film, or against the surface of the
>film gate, for 35mm. On my 2.8E there is a stepped reference surface, again
>moving the back plate towards the lens for 35mm film.
> The two versions of the Rolleikin are not quite the same. For the MX and
>'cord the film plane is very slightly closer to the lens than it is for
>35mm film. On the E it is the same, at least within my ability to measure
>it. By memory, the distance is around 1.5X the thickness of the film and
>paper, or of the 35mm film alone. I posted the measurements of the film
>channel width at the time, must be two or three months ago now, so they
>might be in the archives.
> I was originally under the impression that the back plate moved only to
>clear the Rolleikin arm. In fact, it also does that, but the main reason
>for sliding it is the change the clearance for the film.
> Evidently, the back plate does NOT press the film against the rails.
> I am not quite sure what mechanism is used to locate the film. I did some
>checking on other cameras. My Nikon F also has a film channel and its about
>the same as the channel with the Rolleikin. Ditto for a Kodak 35 camera.
>The main difference between 120 and 35mm is that the 35mm gates have some
>edge guidance.
> My intuition is that 220 film has some more room to flop around in the
>film channel. Its the same thickness as 120 film without the paper, 3.6
>mil., according to a Kodak Tri-X data sheet. I haven't tried to calculate
>whether this is enough to cause film plane problems.
> 35mm film is thicker than 120 but not nearly as thick as 120 plus the
>paper backing.
> ...
>Richard Knoppow
>Los Angeles, CA, USA
>dickburk@ix.netcom.com
From: "Mike Lipphardt" mlipphardt@dynamotors.com>
Newsgroups: rec.photo.equipment.35mm
Subject: Re: film DOfocus etc. Re: Poor Mans Leica ?
Date: Mon, 03 Dec 2001
Not that I can affor it you understand (although I'd dearly love to buy a
RTSIII), there was some testing on the effectiveness of the vacuum back when
the III came out. Results showed that the gain in image quality were
marginal, and variations from frame to frame focusing errors, however
carefully the camera was focused, pretty much drowned out any benefit.
Obviously the benefit is there in theory, but unless you're focusing with
microscopic precision and using a lens with no field curvature at the film
plane, well, I don't think it makes that great a difference.
On the other hand, the RTS series of cameras and their associated lenses are
extraordinary, and well worth owning. I would put down any image quality to
the lenses, and not the back. What I can tell you is that the RTS, 50mm
f1.4 Planar and the 135 f2.8 (all of which I've owned and used) give
fantastic results when properly used. Too bad Contax is so pricy, or rather
too bad I don't make enough money to buy them :)
Mike
"Steve" ss@randomc.com> wrote...
> >Speaking of film flatness, any comments about the Contax vacuum back?
>
> Not from experience, but it seems like a great idea. Forgetting the
> extreme price and lack of available components in the system, I have
> been under the impression that it produces superb images.
>
> Steve
From: "Q.G. de Bakker" qnu@worldonline.nl>
Newsgroups: rec.photo.equipment.35mm
Subject: Re: film DOfocus etc. Re: Poor Mans Leica ?
Date: Mon, 3 Dec 2001
Robert Monaghan wrote:
> a followup point, the lunar hasselblads had rousseau (sp?) plates to help
> eliminate film flatness problems, glass plates with + marks for measuring
> against which the film was pressed (already in a vacuum ;-) to get
> maximally flat film surface.
Apropos Réseau plates: they are a nice tool just because using these, and
knowing the geometrics of the optics used, you do not have to worry about
film flatness issues (and film dimensional stability) that much. You can use
the grid to calculate the true position of each grid point, despite the
image being distorted because it was projected on a non-flat surface. No
matter how flat you try to push the film, it will not be flat anymore once
it has been processed (and you do have to process film before you can do
measurements from it ;-)). So for doing precision measurements you will have
to find a way around that, and using the grid plate helps.
But film flatness remains problematic regarding resolution.
Date: Tue, 04 Dec 2001
To: rollei@mejac.palo-alto.ca.us
From: Richard Knoppow dickburk@ix.netcom.com>
Subject: Re: [Rollei] Right back for 220 TLR? Definite research results
from the home town of Rollei
you wrote:
>O.k. folks,
>
>I checked my 2,8F (selected model), with respect to the depths of the film
>channel for 35 mm and 120 position of the pressure plate.
>
>The pressure plate has 8 pins near to the corners which come in contact
>with other 4 pins located at the frame of the camera. Only one set of 4
>out of the 8 pins of the plate is in action for each position, either for
>the the 35 mm or for the the 120 position. By shifting the plate, it is
>switched between the two sets. When the back is closed, the contact of the
>appropriate four pins of the plate to the four pins of the frame defines
>the depths of the film channel.
>
>And shall I tell you what? The 4 pins of the plate which are in contact
>with the frame in the 35 mm position are shorter than those of the 6x6
>position. This means what? the 35 mm film channel is thinner than the 120
>channel!.
>
>If you want to get this certified, I could go to our original Carl Zeiss
>3D-coordinate measurement machine to obtain precise data for you in 1/100
>of microns. For certified data, my company would charge to you at least a
>rate of =80 100.- per hour for use of the machine. Maybe 90 min would be
>sufficient to obain a protocol, but you should to be safe to calculate 2
>hours. If you convince me to do it on general scientific interest it will
>be free for our beloved RUGers.
>
>The question now is:
> For 220 film: Put the plate into the 35 mm position or not? If the
>thickness of 220 equals 35 mm, I would recommend that.
>
>I will also check whether there are different depths for the 120 and 220
>backs for the 6008 and let you know.
>
>
>
>Best friendly greetings
>
>
>Dirk
My 2.8 E has the two sets of legs exactly as Dirk describes.
220 film is exactly the same thickness as 120 _film_, 3.6 mil acetate
support. 35mm film is coated on 5.0 mil base. Of course, the overall
thickness of 120 film is considerably more due to the paper backing. I
think I posted the measured overall thickness for Verichrome Pan at some
point.
My measurements of the film channel width are indirect. I used a depth
guage to measure the height of the legs from the pressure plate and the
depth of the reference surfaces for them from the film rails. This
indicated that the channel width was less for 35mm film. In both cases I
think I got a width of about twice the film thickness (or for 120 film and
paper thickness). I've discovered from this discussion, or rather its
earlier incarnation, that I didn't understand exactly how the film is kept
flat in the camera. Or more exactly, how it is located to insure its in the
focal plane. If its pushed back against the pressure plate its position
will depend on the thickness of the support, or support and paper backing.
If the position is established by the film rails how is it kept from
buckling in the channel. Rollei lis not the only camera to use this system,
It seems to be universal in 35mm cameras. The difference in position
allowed by the room left in the film channel is not very great, well within
the limits imposed by depth of focus considerations (at least by my
calculations) but still leaves me with an unsatisfied feeling, at least
about my understanding.
I am quite sure I've seen discussions about film guidance systems
somewhere, probably in some optics text, but can't remember where.
In any case, it seems to me that the location of 220 film would be better
if used with the back plate in the 35mm position but that is an intuitive
judgement, not based on actual measurement.
Someone mentioned that Bill Maxwell has measured film position using an
auto-collimator. Those mesurements would be beyond controversy and might
be useful to those who use 220.
----
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com
From: "Leonard Evens" len@math.northwestern.edu>
Newsgroups: rec.photo.equipment.medium-format
Subject: How to think about the effect of film flatness?
Date: Tue, 04 Dec 2001
Perhaps I'm lucky, but in my mainly medium format photography I've never
noticed any major degradation of images due to lack of film flatness. At
one point when I was being somewhat fanatic about such things, I did get
a special back for my Rolleiflex TLR which used a glass plate to insure
flatness, but I've seldom used it.
Still since the issue has been raised in various posts, I've tried to
think about it. I started with the standard formula(s) for depth of
focus, but I've since decided this is the wrong way to approach it. The
problem is that the same simple geometric considerations---i.e., similar
triangles---used to derive formulas for depth of focus are also used to
derive formulas for depth of field. so one can't use these formulas as
though they were independent of one another.
I've come up with another way of thinking about it, and I wonder if
others think it makes any sense.
If the film is not flat, then some parts of it are not in the expected
film plane. That is equivalent to focusing the lens at a different
distance for that part of the film. That could either bring that part
of the image into better focus or it could put it further out of focus.
This obviously will have some effect on depth of field, as it appears in
different parts of the image. But getting a quantitative idea of its
effect requires posing the problem correctly. I have some initial ideas
about that, but I'm not sure how useful they are. Anyway, here they
are.
Assume one is doing normal photography with typical lenses and one
focuses on the hyperfocal distance. Then some back of the envelope
calculations seem to show that the distance of the image plane from the
focal plane is about C*N where C is the diameter of the circle of
confusion and N is the f-number. (Let's ignore diffraction for the
purposes of these calculations.) So it seems to me the natural unit for
thinking about film flatness is C. If the deviation from flatness is
just a small multiple of C, it would seem the effect on depth of field
would be minimal. But clearly if it were high, e.g., N/3 times C, it
would be pretty dramatic.
Does this make any sense? If so, what does it say about film flatness
as a problem for different formats? For example, one might conclude
that in some sense, the larger the format the less the potential problem.
The argument would be that the larger the format, the larger the
acceptable C, so the larger the acceptable absolute measure of
displacement from flatness. Also, with larger formats, one tends to use
higher f-number, both to achieve adequate depth of field and because
such f-numbers don't create diffraction problems as they would with
smaller formats (and smaller Cs).
I stand ready to be corrected for any faults in my reasoning. Also,
what are typical numbers for departures from flatness for various
formats. Clearly, the smaller the format, the easier it should be to
control flatness, at least up to a point. But how much easier is it?
--
Leonard Evens len@math.northwestern.edu 847-491-5537
Dept. of Mathematics, Northwestern Univ., Evanston, IL 60208
Newsgroups: rec.photo.equipment.medium-format
From: Andrew Koenig ark@research.att.com>
Subject: Re: How to think about the effect of film flatness?
Date: Tue, 4 Dec 2001
Leonard> If the film is not flat, then some parts of it are not in the
Leonard> expected film plane. That is equivalent to focusing the lens
Leonard> at a different distance for that part of the film. That
Leonard> could either bring that part of the image into better focus
Leonard> or it could put it further out of focus. This obviously will
Leonard> have some effect on depth of field, as it appears in
Leonard> different parts of the image. But getting a quantitative
Leonard> idea of its effect requires posing the problem correctly.
I wonder if the following way of looking at it will help.
Imagine that the film is in the right place, and look at one point
on the sharply focused image. Light from all parts of the lens must
be reaching that same point; otherwise it wouldn't be a point.
Now displace the film slightly. The light that had been reaching a
single point will now fill a circle, called the circle of confusion,
the perimeter of which can be determined by drawing straight lines
from the original point to all the points on the edge of the lens
diaphragm as seen from the film.
In other words, suppose the correct lens-to-film distance is F,
the exit pupil--that is, the diameter of the lens as seen from the
film--is E, and you displace the film by a distance D. Then the
diameter of the resulting circle of confusion will be D*E/F.
Note that (D*E)/F is equivalent to D*(E/F), so the parentheses don't
matter. Note further that E/F is nothing more than the reciprocal of
the aperture, at least for symmetric lenses (I'm not quite sure how to
account for asymmetric lenses, such as retrofocus lenses, but I would
not be surprised to find that it doesn't matter).
So we have a simple rule: Divide the deviation from film flatness by
the aperture and you have the circle of confusion. For example, a
displacement of 0.1mm at f/4 will yield a circle of confusion of 0.025mm.
--
Andrew Koenig, ark@research.att.com, http://www.research.att.com/info/ark
From: Struan Gray struan.gray@sljus.lu.se>
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: How to think about the effect of film flatness?
Date: 4 Dec 2001
Andrew Koenig, ark@research.att.com writes:
>Leonard> If the film is not flat, then some parts of it are not in the
>Leonard> expected film plane. That is equivalent to focusing the lens
>Leonard> at a different distance for that part of the film. That
>Leonard> could either bring that part of the image into better focus
>Leonard> or it could put it further out of focus. This obviously will
>Leonard> have some effect on depth of field, as it appears in
>Leonard> different parts of the image. But getting a quantitative
>Leonard> idea of its effect requires posing the problem correctly.
>
> I wonder if the following way of looking at it will help....
Readers might want to look at this diagram:
http://www.sljus.lu.se/People/Struan/pics/dofconfuse.jpg
The top diagram illustrates the conventional way of calculating
DOF, as described in Andrew's post. The extension to a buckled film
should be obvious.
The lower diagram might amuse DoF afficionados. It occurred to me
that the conventional derivation, while great for considering buckled
film, was actually misleading for the usual case of a photographer who
has focussed on one thing and wants to know what else will be 'in
focus'. If you look at the light from the far DoF limit plane (green)
in the top diagram, you see that on-film it is actually spread out by
*more* than the circle of confusion. Similarly, the light from the
near DoF limit is spread out on the film by *less* than the circle of
confusion.
The lower diagram adjusts the position of the near and far DoF
planes so that on-axis points create a spread on the film equal to the
circle of confusion. If you churn through the trig, you find that the
new near DoF is almost exactly the same as the old one, but that the
far DoF doesn't recede to infinity quite as fast as the old one did
when the lens is stopped down. I have convinced myself that some of
my hyperfocal-distance landscapes with surprisingly blurred distant
mountains are due to this mismatch.
Mind you, it's completely cured by stopping down one more stop for
safety.
Struan
From: Struan Gray struan.gray@sljus.lu.se>
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: How to think about the effect of film flatness?
Date: 5 Dec 2001
Leonard Evens, len@math.northwestern.edu writes:
>> I wrote:
>>
>> Readers might want to look at this diagram:
>>
>> http://www.sljus.lu.se/People/Struan/pics/dofconfuse.jpg
>>
>> The top diagram illustrates the conventional way of calculating
>> DOF, as described in Andrew's post. The extension to a buckled film
>> should be obvious.
>
> I'm afraid I don't recognize that diagram. The bottom diagram is the
> one I'm familar with.
Lucky for you. The books I have all use the top diagram, as do
all the internet sources I have looked at closely. They confused the
hell out of me when I started to trying to figure out what these DoF
discussions were all about.
The idea is that the light from an on-axis point source forms a
cone behind the lens, with its base formed by the exit pupil and its
point at the focal plane. It then spreads out in a second cone behind
the focal plane. If the film moves away from the focal plane, the
light will form a circle on it rather than a point. Once you have
defined an 'acceptable' circle of confusion, that then translates into
an allowable movement of the film. The end points of that allowable
movement define new image planes, which you translate into positions
in front of the lens using the Gaussian formula.
That all makes sense in terms of film movement, but the same
argument and diagram are often given to derive DoF. In my readings,
'often' means 'always', and although I am happy to accept that might
say as much about my readings as it does about the world of
photography, I have seen the argument presented many, many times.
The formulea given by the two methods are very close for all
likely photographic situations. I plugged them into an analysis
package I use and plotted DoF limits for various combinations of focal
length, aperture and object distance. The only practical difference I
could find was the one I mentioned: if you take a landscape and focus
on the hyperfocal distance given by the first diagram, your horizon
will be blurred by more than you expected.
> The second diagram is what I use to derive the
> formulas for depth of field. However, the exact
> formulas one gets this way are a trifle complicated
> and one usually simplifies them by assuming
> the object distance is large compared to the
> focal length.
If you assume that you know the actual f-number the formulea are
not too bad. They certainly allow you to play with parameters and see
what is important and what is not. For any given lens, you should
work out what the f-number really is (often called the 'effective
aperture' in photography books), but outside the macro range it
doesn't change enough to worry about.
> I would like to see why it is true from a
> theoretical point of view.
Me too, so bugger the armchair beer swillers who think an interest
in mathematics precludes an interest in art. They are simply misled
by their own inability to engage in more than one mental function at a
time into thinking that it is a universal affliction.
> Not only would the theory be enlightening, but it
> would give a way to understand quantitatively how
> large a departure from film flatness is acceptable
> as it relates to format size.
For a true quantitative understanding you need to add diffraction
and aberrations to the mix. Diffraction can be treated analytically,
especially if you don't mind jumping into Fourier space, but
aberrations quickly lead you into a morass of special cases and
empiricisim. Worse, the effects of aberrations are such that choosing
'best focus' becomes a subjective issue, and 'acceptable' depends on
whether you like sharpened edges or softly-glowing highlights.
There are freeware or demo ray-tracing packages if you want to get
into this in detail, but for practical photography outside of the
technical and scientific realm, remembering the relationships between
quantities is more important than knowing exact values for the
prefactors in the equations.
In the case of film bulge, Bob M's page gives numbers and facts
for a variety of cameras and photographic situations. It's no
accident that those doing photogrammetry or film-based remote sensing
take great care to keep the film flat. It is also no accident that in
almost all scientific imaging outside wide-area survey problems the
field has been taken over by nice, flat CCD chips.
I personally regard film bulge in the same way I regard
reciprocity failure. It's one of those things that is irrelevant for
almost all my photography, but worth konwing about for those (very)
few occasions where it can ruin the shot.
Struan
From: john@stafford.net (John Stafford)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: How to think about the effect of film flatness?
Date: 5 Dec 2001
Seems rather intuitive to me. You are using a (nominal) normal lens
on a camera. Focus on an object. Then turn your focusing mount out
.006". The image will be thrown out of focus to some degree. That's
happening in your camera when the film isn't flat. Stopping down is
covering the effect, so shoot a dozen or so rolls wide open at closer
ranges. If you can't see the consequences of non-flat film, then
there's nothing to worry about.
:) I chose .006" above because that's the best tolerance I can made
when planing wood, for example when I hacked out my super-wide,
bellowless 5x4. Rather arbitrary, maybe too big a number for
film-flatness, but it illustrates the point.
I do appreciate your math, Professor. Maybe you could be our Martin
Gardiner of Photography. Did you know that every mechanical 3-number
dial combination lock has two different combinations? Oh. I think I
learned that from you. :) -5, +2.5
Date: Fri, 07 Dec 2001
To: rollei@mejac.palo-alto.ca.us
From: Dirk-Roger Schmitt Dirk-Roger.Schmitt@dlr.de>
Subject: [Rollei] Right back for 220 TLR? Further research results
New research:
Well, I also checked the 120 back and 220 back for my 6008. And:
surprising, surprising: There are nearly the same distance pins at the
pressure plate as I described for the 2,8F. And: The pins at the pressure
plate for 220 film are shorter than the ones for 120. That means that the
film channel for 220 is thinner than for 120.
Everythink clear for everybody?
Still open question: Which is the right plate postion for 220 at the TLRs?
Best greetings
Dirk
you wrote:
>O.k. folks,
>
>I checked my 2,8F (selected model), with respect to the depths of the film
>channel for 35 mm and 120 position of the pressure plate.
>
>The pressure plate has 8 pins near to the corners which come in contact
>with other 4 pins located at the frame of the camera. Only one set of 4
>out of the 8 pins of the plate is in action for each position, either for
>the the 35 mm or for the the 120 position. By shifting the plate, it is
>switched between the two sets. When the back is closed, the contact of the
>appropriate four pins of the plate to the four pins of the frame defines
>the depths of the film channel.
>
>And shall I tell you what? The 4 pins of the plate which are in contact
>with the frame in the 35 mm position are shorter than those of the 6x6
>position. This means what? the 35 mm film channel is thinner than the 120
>channel!.
>
>If you want to get this certified, I could go to our original Carl Zeiss
>3D-coordinate measurement machine to obtain precise data for you in 1/100
>of microns. For certified data, my company would charge to you at least a
>rate of =80 100.- per hour for use of the machine. Maybe 90 min would be
>sufficient to obain a protocol, but you should to be safe to calculate 2
>hours. If you convince me to do it on general scientific interrest it will
>be free for our beloved RUGers.
>
>The question now is:
> For 220 film: Put the plate into the 35 mm position or not? If the
> thickness of 220 equals 35 mm, I would recommend that.
>
>I will also check whether there are different depths for the 120 and 220
>backs for the 6008 and let you know.
>
>Best friendly greetings
>
>Dirk
>
>In my 2.8 F it reduces the depth of the film channel, I thought so=20
>far. But I shall double check it and let you know the findings.
>
>Dirk
>
you wrote:
>>Dirk,
>>
>>We went through this several weeks ago. The 35mm position moves the
>>plate to avoid collision with elements of the Rolleikin devices. It does
>>NOT reduce the depth of the film channel for 120/220 film.
>>
>>The 6x6 position is the correct one for 220 film.
>>
>>
>>Best Regards,
>>
>>David Seifert
>>dseifert@absolute.net
>>
>> you wrote:
>>>nope, you have to switch into the 35 mm position as the 220 film has
>>>the same thickness as the 24x36 film due the missing paper.
>>>
>>>Dirk
>>>
>>>
>>>
>>>
>>> you wrote:
>>>>I had the same reaction when I first opened my 2.8F, having had a number
>>>>of other roll film cameras which used two-position pressure plates for
>>>>120 and 220. But apparently Rollei never felt the need for this - you
>>>>just leave the pressure plate in the 6x6 position.
>>>>
>>>>Cheers,
>>>>Kip
>>>>
>>>>"Joe B." wrote, in part:
>>>> >
>>>> > I've just got a 3.5F type 4 with built-in 220 option. But I notice
>>>> there is no
>>>> > reference to 220 film inside the back- the two positions for the
>>>> pressure plate
>>>> > say
>>>> >
>>>> > 6 x 6 cm 2 1/4 x 2 1/4"
>>>> >
>>>> > and
>>>> >
>>>> > 24 x 36 mm
From: largformat@aol.com (Largformat)
Newsgroups: rec.photo.equipment.large-format
Date: 09 Dec 2001
Subject: Film Holder flatness
There has been a lot of debate on this forum about how well different film
holders hold film flat. Several years ago we did a study about this and the
Grafmatic holders scored the best. These are only available used - in the price
range of 80-120 each. This article was done before the Kodak single sheet
Readyload products became available. These holders will accept any of the
currently available 4x5 films so you have complete freedom in selecting a film.
I have had some of these Grafmatics for 20+ years, all bought used, and never
had a problem with them jamming or the septums fgetting bent. If you buy some
make sure you get a 10 day MBG in case they do not work.
With regards to the new crop of Readyload and Quickload holders we found that
they both can be used with either the new Kodak single sheet film packs or the
Fuji Quickload packs.
Here are my thoughts. If you already own a new Polaroid holder and want to use
the single sheet Kodak Readyload films or the Fuji Quickload films try them in
the Polaoid holder first. Our expereince is that this works fine. If it does
not work for you then get whichever holder matches the brand of film you will
be using.
steve simmons
From: flexaret2@aol.com (FLEXARET2)
Newsgroups: rec.photo.equipment.medium-format
Date: 01 Jan 2002
Subject: Re: How to think about the effect of film flatness?
At a Photo Expo I met one of the experts at the Kyocera booth to discuss the
Contax 645. While realizing he had an axe to grind to promote his product, I
feel he did speak truthfully to me when he said-
"The medium format lack of film flatness is the best kept secret in the
photographic industry."
He told me that his company's Contax 645 had partially solved that problem, but
only in their vacuum back - which only took 220 film, as it would not work with
the backing paper on 120 film.
If I ran a business where film plane flatness was a critical issue
I would buy and use a Contax 645 with that back and 220 film.
I have been examining a variety of cameras old and new to see
how that problem is dealt with.
You can read my articles on Bob Monaghan's Medium Format/Bronica site-
http://people.smu.edu/rmonagha/bronica.html
My short conclusions - the current Rollei 6x6cm SLR cameras -very flat film
plane. On the Pentax 67 - very flat film plane.
On less expensive equipment - Bronica S2A with 12/24 back and
improved one top roller film insert (sometimes marked "A") - very flat film
plane - so that I can use my adapted 180MM f2.8 Sonnar wide open
and get sharp portraits with the background blurred out.
New Kiev NT backs - available in Kiev 88 and Hasselblad versions
for under $99 - very flat film plane.
Other manufacturers have dealt with this in various ways, better or worse. If
the user wants to shoot with wider apertures and still get sharp pictures, he
should not be forced to stop down and lose a creative effect to make up for the
lack of a flat film plane.
- Sam Sherman
From Rangefinder Mailing List:
Date: Fri, 31 Aug 2001
From: Dave Saalsaa SaalsD@cni-usa.com
Subject: Re: [RF List] Way OT: Large format
> Hi John,
I think since you are after fine grain and the abilty to enlarge your
photos really big, you might want to consider medium format. I do use a 4
X 5 camera in studio but for much of my work I use a 6X7 film back to cut
cost of film and processing and to actually get a flatter film plane with
the 6 X 7 film holder with it's pressure plate holding the film flatter
for better edge to edge focus. A 4 X 5 film will distort or bow quite a
bit when you have the camera on it's nose for copy shots or table top
photos. I have found the 6 X 7 to give better results because of this.
But I use the view camera because of it's perspective control with it's
tilt and shift controls. The Pentax 67 could very well be the camera you
are looking for with it's large neg. and superb optics. It would be much
easier to lug around than a view camera. JMHO
Dave Saalsaa
Date: Wed, 24 Oct 2001
From: Gene Johnson genej2@home.com
To: cameramakers@rosebud.opusis.com
Subject: [Cameramakers] Re:Air Force Recon Cameras/ film flattening
William and George,
I don't have any direct knowledge of any nine inch roll film cameras,
but the 5 inch cameras I know of all have vacuum film platens. The
KS-87b, KA-93,KA-90,KA-95,KA-96, and KS-127 all use vacuum with the
spec being 1-8 inches of Hg, at a min of .25 cfm airflow. These cameras
typically operate in the 65-85 lp/mm resolution range with Kodak plus-x
aero film.
Gene Johnson
Date: Wed, 24 Oct 2001
To: cameramakers@rosebud.opusis.com
From: Robert Mueller r.mueller@fz-juelich.de>
Subject: Re: [Cameramakers] Re:Air Force Recon Cameras/ film flattening
And I have encountered types with glass in front of the platen, so both
possibilities are in use.
Bob
From camera makers mailing list:
From: "Brian Swale" bj@caverock.net.nz
Date: Mon, 22 Oct 2001
Subject: [Cameramakers] Re Glass platen etc
Hi all,
Thanks for all the information and ideas.
Schott Glass; yes I DID find their site and had a good look through it,
but it
is large and clearly the mirogard glass escaped my notice, Markus.
Michael King, Yes, you have a point there about people such as me getting
side-tracked into such as camera construction when maybe the game really
is taking photos.
Some people obviously like doing both and are good at both. However, what
has sent ME on this quest is this.
I have several of John Shaw's books. "Closeups in Nature" is one I have
beside me as I write.
And I look at his photos and think 'Hey, I'd like to take photos as nice
as his - and as sharp'.
Because I like sharp photos too, if that is part of the effect I want -
which usually it is.
And I have followed his advice. Ten years ago I bought the Gitzo tripod and
manfrotto = bogen head he recommended and never for one moment
regretted doing so, even though they cost and arm and a leg to import them
from a camera store in New York..
I use Olympus gear for most of my 35mm work and he uses Nikon, but I
figured - if I use the best Zuiko lenses (and some have GREAT tests in the
journals) I must get results something close to his in quality.
Well, sadly, no. Not. And I wonder why.
I have also in the last few months discovered several of the discussion
groups such as this, and have learned a lot more as a result. And that is why
I wonder about film flatness; and putting a glass platen in an Olympus
camera - as well as medium format - of which I now have several press
versions as well as a Linhof.
Glass platens are clearly still in favour. Last night just for fun I did a search
on Google (http://www.google.com) and came up with these sites which
could be of interest for the ideas and info they contain.
http://mac.usgs.gov/mac/tsb/osl/acspecs.html
http://www.nrc.ca/inms/calserv/dsopte.html
http://mac.usgs.gov/mac/tsb/osl/pricelist.html
And some time before I saved this article - but didn't code in the uRL as I
usually do
"Focus problems in medium format: The article they wouldn't (didn't dare to)
print" by John Petterson a medium-format repairman with Christian Photo,
Des Moines, Iowa. e-mail askcmraguy@aol.com
(Do a search on Google should find it)
He has found that bad (= soft ) focus problems in many professional
cameras ( including such as H*s*e*b*a*) can be fixed by increasing the
spring strength behind the pressure plate. The springs lose tension badly
over time, apparently.
There are almost certainly several answers to this technical problem.
Cheers, Brian
Brian Swale e-mail bj@caverock.net.nz
[Editor's note: see http://www.a1.nl/phomepag/markerink/mf_focus.htm ]
From: hemi4268@aol.com (Hemi4268)
Newsgroups: rec.photo.equipment.medium-format
Date: 05 Feb 2003
Subject: Re: Q: Mamiya RZ lens resolution?
>Try to find out the criteria used by NASA when they were shopping for
>camera systems to use in space - should give you a starting point.
>
I can't say anything about NASA but since I was chief of the CIA spy camera
program from 1985 to 1996 now retired I might have a few insights.
First, just about all name brand lenses have about the same resolution although
for special applications, suppliers would allow us to source select. This
means we would take delivery of say ten 180mm lenses and select 5 sending the
rest back.
Biggest issue was with the camera bodies. Only about 2 out of 10 camera bodies
focused well enough to meet specs. This means the other 8 camera bodies had
mirrors that were not in sync with true focus. In other words, when you
focused on something at 20 ft you were actually focused at 16 or maybe 25 ft.
This is a full 100 micron focus error that won't really clear up until stopped
down to at least f11.
Just about all image quality problems can be traced to the camera bodies. It's
very rare indeed to trace image quality problems to a lens from a major
manufacture.
Larry
