I have written in the past about the problem
with film un-flatness in medium format cameras and the resulting loss
of sharpness therefrom. I have also come up with suggestions to improve
film flatness and image sharpness in Bronica S2A and other cameras - see
Bob Monaghan's Classic Bronica website
and film flatness pages.
| 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"] |
In the November 2000 issue of Popular Photography there is a small article
entitled- "Is Rollfilm 220 better than 120 for film flatness?"
This article is reprinted from Zeiss Camera Lens News
#10 and the article
omits to state that the Contax 645 does take sharper pictures on 220 film,
but only because it has a vacuum pressure plate back that can hold that
film flatter than 120, which no other camera has.
Some excerpts from the article follow-
"Zeiss has now developed a new measuring system to evaluate film flatness
in medium-format photography. The new system is based on a computerized
microscope that can automatically scan and focus on multiple points of a
film frame in a medium-format camera magazine. ....... from these findings
Zeiss can draw conclusions about the field flatness required for medium
format lenses, and trace causes for lack of sharpness in customer's
photos. ........ attributed to misalignments of critical components in
camera, viewfinder, or magazine; focus errors; camera vibrations; film
curvature; and a variety of reasons. ..... 220-type rollfilm usually
offers two times better flatness than 120 type.........."
The article goes on to blame rollers in medium format magazines for
causing a "bend" in the film and suggests a roll of film be shot quickly
before each frame has had a chance to take a "bend" at the rollers.
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:
It is taking me over 2 weeks to get a roll of developed and proofed 220
film back from my local pro lab.
They are presently so busy that on some days they process over 700 rolls
of film per day!
You did not mis-read that - 700 rolls of 120/220 film per day - right here
in New Jersey.
- Sam Sherman
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
was at
http://www.zeiss.de/de/photo/home_e.nsf/allBySubject/Launch+-+Zeiss-engl+JavaNavigator
[Ed. note: now link checker reports not found as of 2/2003, check with the http://www.zeiss.de
page for links to Zeiss Camera Lens News issues now being published online...]
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?
Later,
Owl
Dr John Owlett
Senior Internet Security Consultant, IBM Global Services
[email protected] http://www.ibm.com/security/services/