[rollei_list] Re: Tripod versus Handheld
- From: CarlosMFreaza <cmfreaza@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Thu, 18 Aug 2011 19:59:58 -0300
The CZ test results were published in Camera Lens News nº 10 from
Summer 2000, I reproduce the article:
"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."
Camera Lens News No. 10, Summer 2000
2011/8/18 Allen Zak <azak@xxxxxxxxxxxxxxx>:
>> Some Carl
>> Zeiss tests showed a significant sharpness difference for 120 and 220
>> film (220 film was better) due to the 120 film paper back action on
>> the film strip.
>>
>> Carlos
>>
>
> That was the primary reason both my Rolleis were modified to accept 220,
> which I used for all my MF photography, except when a particular film was
> available only in 120. Now, very few of the emulsions I prefer are
> available in 220. Apparently, this is just another burden of getting older.
>
> Allen Zak
>
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