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From: [email protected] (BHilton665)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: hyperfocal chart of 67 lenses?
Date: 28 Oct 1998
>From: [email protected] (DRemien) > >Where can I find hyperfocal data for 67 lenses? Specifically the 55-100 >range >for the new Pentax 67 zoom lens.
Hyperfocal depends on the size of the lens, f/stop and the size of your
chosen circle of confusion (or at least as I understand it ... if I'm
wrong I'm sure to hear about it here!). So it would be the same as any
other 55 or 100 mm lens and format ... except I've found you can go with a
larger circle of confusion on medium format since you don't have to blow
it up as much to get a given print size.
Here's a formula I copied from a book by Craig and Nadine Blacklock for
doing the calculation ... I have it in a spreadsheet form and use it to
calculate this for 1/800 inch and 1/1000 inch circles of confusion. Comes
in very handy in the field. I think the distance scale on most lenses is
based on 1/800 inch, which I think roughly correlates to an 8 x 10 print.
For sure I can use 1/1000 inch and get excellent blow ups from medium
format up to 16 x 20 though.
Here's the formula ...
hyperfocal distance in inches = (mm of focal length * mm of focal length /
625)/(f/stop * circle of confusion size in inches)
So for a 100 mm lens at f/22 and coc = 1/1000 inch it would be
(100*100/625)/(22*.001) = 727 inches = 60.6 ft. So you would be in focus
from just over 30 ft to infinity if I've done the calculations right ...
At the more normal coc of 1/800 inch the hyperfocal is 48.5 ft.
Since it's tough to do this without an error, or since I may be off in
assuming it's the same formula regardless of format, or since others may
have different definitions of hyperfocal than the Blacklocks, let those
flames and constructive criticisms start right here ___________
(grin)
Date: Wed, 28 Oct 1998
From: [email protected] (Rudy Garcia)
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Focussing hyperfocal or infinity
[email protected] (Martin
Tai) wrote:
> Paul van Walree ([email protected]) wrote: > : Nick Fiduccia wrote: > : > : > You are right, I focus at infinity when doing landscapes. Not many > : > people know this > > : Of course not. Likewise, you don't know what I focus at. > > : > and focus on the hyperfocal distance and infinity > : > comes out not very sharp. Most people will then reply to close > : > down a couple of stops. However, I read somewhere that you would > : > have to close down about 6 stops(!) to get good sharpness with > : > todays optics and films. > > : That depends on the definition of sharpness. The classic rule that an > : image is sharp when the circles of confusion on the negative are smaller > : than 1/30 mm, is in no way affected by whatever lens design or film type. > : Many people, like you and me, find this rule superseded and strive after > : the best possible sharpness. Maybe stopping down 6 stops (from what?) may > : give the DOF one desires, but it's not very smart since the overall sharpness > : decreases when stopping down to much. > > : Walrus > > > Not many people knows about Dr. Harold Merklinger's book "The INs and > OUTs of FOCUS". > In this book he discussed the merit of focusing at infinity vs > focusing at hyperfocal distance. > If distant objects are important in your composition, focus at infinity > is the way to go, it provides much more factual depth of field. If near > object is more important, then focus on the object or focus at hyperfocal. > > Focus at infinity gives a much smaller blur spot for distant object. > > Example, 50mm lens at f8, hyperfocal = 9.38 meter, the following > is a table of blur spot sizes of hyperfocusing vs infinity-focusing > > > > Object Distance Focus at Hyperfocal | Infinity > meter > > 3 0.072 0.11 > 9 0.001 0.04 > 20 0.018 0.02 > 50 0.027 0.01 > 100 0.03 0.008 > 1000 0.033 0.005 > > > It is evident, hyperfocusing renders near objects within 20 meters > (about twice the hyperfocus distance ) sharper then infinity focusing; > But for object beyond 2 x hyperfocal distance, infinity focusing is > much sharper. > For example, at 1000 meter, the blur spot of hyperfocusing is 0.033 mm > that corresponds to only 30 lines/mm; while the blur spot size for > infinity focusing is 0.005mm , corresponding to 200 lines per mm, > about 7 times sharper then hyperfocusing. > > In this example, the sharp zone of hyerfocus is really only from > about 5 meter to 20 meter, a depth of 15 meter > On the other hand, the sharp zone of infinity focusing is from 20 > meter to 1000 meter and beyond. > > The problem with hyperfocusing is that its circle of confusion > increases with distance toward 0.033 limit. > While with infinity focusing, the blur spot decreases with distance > until it reaches the diffraction limit ( about 200 lines/mm at f8) > > I focus at infinity for all my landscape, street scene pictures, > even with Minox 8x11mm format camera, great depth of field. > > Harold Merklinger has a website; you may search for it with Yahoo. > > martin tai
A few of comments on the above are in order.
Focusing at the hyperfocal distance maximizes the depth of field (from
half the hyperfocal distance to infinity). Focusing at infinity wastes a
lot of the DOF, as there is nothing worth shooting at distances beyond
infinity. What focusing on the hyperfocal distance does is to maximize
the near-far distance objects that will be rendered will an acceptable
focus, as defined by the allowable circle of confusion.
Most interesting landscapes have a near, mid and far area with subjects in
their composition. I think that unless there are compelling artistic
reasons for having the near and mid subjects badly out of focus, whilst
the far subjects are in focus, such images will not be appreciated.
Last, but not least, the above theoretical calculations do not take into
account the scaling of subjects relative to the camera. A person or
similar size object 100 to 1000 meters away, shot with a 50mm lens
subtends a pretty small angle. Why would any one care how sharp each
point on the person's face is rendered on the film, if such a large
enlargement would be needed to discern the person's face, as to have the
film grain make the excercize useless?
Anyway, thats my $0.02 worth.
--
Use address below for Email replies. Address on Header is bogus to defeat
AutoSPAM.
[email protected]
________________________________
Rudy Garcia
From Nikon Digest:
Date: Wed, 4 Nov 1998
From: "David S. Cox" [email protected]
Subject: Re: Hyperfocal Distance
Regarding the recent thread on calculating hyperfocal distabce and deploring
the lack of DOF scales on Nikon zoom lenses, it is not necessary in practice
to use fancy mathematical calculations to determine the hyperfocal distance.
It may very easily be calculated by dividing the focal length of the lens in
millimeters by 10 and squaring the result. The final result is a very close
approximation to the hyperfocal distance in feet at f/11. This calculation
is based on a circle of confusion of 0.03mm, which is close to normal for
the 35mm format. The HFD at f/11 can be converted to other apertures as
follows:
HFD @ f/5.6 = HFD @ 11 x 2
HFD @ f/8 = HFD @ f/11 x 1.5
HFD @ f/16 = HFD @ f/11 x 0.7
HFD @ f/22 = HFD @ f/11 x 0.5
While only a close approximation, the results of this simple calculation are
more than accurate enough, given the difficulty in setting precise distances
on most lens' focussing scales. Actually, I have written out a small table
of hyperfocal distances for each of my lenses on a self-adhesive label which
I have fastened to the inside of the lens cap so it is always available for
quick reference.
BTW, the formula for calculation of precise HFD's, should you need them, is
as follows:
HFD (in mm) = (focal lenth of lens (mm))^2/Diameter of cicle of confusion
(mm) x f/ stop
The best circle of confusion diameter to use is 0.025mm or 0.03mm for the
35mm format. Some people use 1000th. of the focal length, but this is a
very low standard of sharpness for lenses over 35mm focal length. The
result of the above calculation is the HFD in millimeters. It needs to be
converted to feet by dividing by 300.
Hope this is of help.
- ---
David S. Cox
[email protected]
rec.photo.technique.misc
From: "Pat Warnshuis" [email protected]
[1] Hyperfocal Distance
Date: Sun Feb 07 15:01:12 CST 1999
Thom Hogan's formula for hyperfocal distance
(Nikon Field Guid, p234) is stated as
(F X F)/(f x F x .001)
Where F is focal length and f is the aperture.
A simplification of this formula (allowing for
unaccountable errors which build up below 35mm) is
H = 3.3 x F/f
Where:
H = hyperfocal distance in feet
F = Focal length of the lens in mm
f = aperture (nondimensional)
(I know I have mixed dimensions here but I have
included the conversion factors so we can use
the more familiar mm for the lens and feet for
the distance.)
If you apply these figures to a 80mm lens at f-8,
for example, you will get an hyperfocal distance of
3.3 x 80/8 = 33.3 feet
and a 100mm at f-16 is
3.3 x 100/16 = 21 feet
An additional simplification for field work is that at
f-16 the distance from 1/2 the hyperfocal distance
to infinity is "in focus". So, for landscapes, if
you settle for f-16 as a standard aperture, all you
need remember for both hyperfocal distance and DN
(near focus point to infinity) is
H = 0.2 x F !!! (H in feet, Focal length in mm)
DN = 0.1 x F
I don't know why Thom's formula does not work
with his own hyperfocal distances (p98) for lenses
below 50mm. He is not using a constant circle of
confusion, but the term F/1000.
good luck
....patrick