Related Postings:
Film Flatness
Issues
Related Articles by Sam Sherman:
Medium Format Film - Flatness or Not?
In Search of Crisp Images...
MF Film Flatness
Issues
Bronica S2A Film
Back Insert Variations
Bronica S2/A Film Back Variations
Bronica Focus Problem - And How to Solve
It
| 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"] |
This is a followup to other writings I have done on this subject.
Old Bronica S2A cameras in excellent working condition, with good
condition
Nikkor optics and their
finder foam replaced and aligned can take super-sharp photos rivalling
expensive new Hasselblad and
other medium format cameras.
One more item to check is the film inserts in the backs.
Obviously Bronica studied their film inserts which were the same for all
"C"
cameras plus "S2" and "S2A" with
12/24 exposure backs (120/220).
Closely examining these backs one can see major improvements made to them,
although all versions interchange
with the above cameras. Beware - they are not all the same.
Note:
1- The Early Version Inserts (type one) -Have Two rollers where the film
rolls onto the takeup spool and the top and bottom rollers seem to be
anodized black. The instructive test is usually in black letters on gold
background.
2- Later Version Inserts (type two)- Have only One roller at the top where
the film rolls onto the takeup spool and
the top and bottom rollers are finished in Grey with a Teflon-like
anti-stick coating. The instructive text is usually
in silver or white letters on a black background. The letter "A" (not The
Scarlet Letter) is sometimes embossed on the
side of the insert indicating it to be a later model for S2A cameras-
which will also work in C and S2.
3- There are in between variants of these two major types having some
characteristics of both.
It is important to clean these inserts thoroughly and drop some light oil
into all roller pivots.
My initial tests showed the Type Two inserts to produce a much flatter
film plane for sharper images. Now, I have done a conclusive test.
Some years ago Modern Photography took some Hasselblad backs with
film in them, removed the dark slides and projected grid patterns on the
film in the apertures of the backs. All kinds of film bulging and rippling
was noted, indicating these backs did not produce a flat film plane and at
wide apertures unsharp images would result. That is why it was necessary
with Hasselblad and other medium format cameras to stop the lenses down to
allow for depth of field to cover up the unsharp images that these backs
would cause..
Next I turned the back's wind knob until I reached number one. It was hard
to turn. The knob locked at number one
so I had to insert a screwdriver into the slot on the back to release the
wind knob and then turn to number two.
With this Type One insert - it was hard to turn the knob and I did this
throughout the roll until I wound the film up.
The film in the back's aperture was rippling badly and pressing a finger
against it allowed me to push the film down against the pressure plate,
indicating it was bulging badly - not a flat film plane.
Also important to note - these Type One inserts were hard to wind and must
have contributed to wearing out the
wind gears in S2 and C models.
The film in the aperture did not bulge (to any great degree) and was lying
flat against the pressure plate. The whole roll of film wound smoothly
until it took up on the takeup spool.