[rollei_list] Re: 220 vs 120 film flatness
- From: CarlosMFreaza <cmfreaza@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Fri, 30 Apr 2010 16:14:35 -0300
Interesting data Emmanuel. When 220 film appeared in 1965, Rollei R&D
tried the new film in the TLR, they concluded that 220 film not only
could work without TLR cameras film guidance modifications, it also
eliminated any film flatness issue. It was not necessary a special
position for the film pressure plate.
There is a perceptible difference when you use 220 film regarding 120,
with 220 the film transport mechanism works so light that you doubt if
the camera has film inside, it seems to "float" as you wrote.
I did not notice a minimal sharpness difference between 220 and 120 films.
All the best
Carlos
2010/4/30 Emmanuel Bigler <Emmanuel.Bigler@xxxxxxxx>:
> CarlosMFreaza a écrit :
>>
>> Carl Zeiss did a research about the film flatness using 220 and 120 film:
>>
>> http://tinyurl.com/35kmksu
>>
>>
>> http://www.zeiss.de/C12567A8003B58B9/ContentsWWWIntern/134AEE504E89CD50C12569620039712C
>>
>
> Carlos ! And you could survive for 10 years without using 220 rollfilm,
> since apparently you missed this article by Zeiss dated year 2000 ? ;-);-)
>
> The problem apparently came with some fast lenses, in the style of f/2
> designed for the Contax 645 camera.
> With our beloved Rollei TLR stopped down to their best aperture, f/8 or
> f/11, you can sleep quietly : the allowed depth-of-focus is plus or minus 8
> to 11 times yout favourite circle of least confusion ; I know that you use
> something like 25 microns to compute your depth-of-field tables, in order to
> get images in 6x6 that are top-class, it means that you can allow flatness
> defects of about plus or minus 200 to 300 microns.
>
> If the flatness problem was really an issue, Chris Perez could never find
> on-film resolutions close to 100 cy/mm with a good old 120 rollfilm on
> either a Rollei TLR or an Hasselblad with a 120 film back...
> http://www.hevanet.com/cperez/test/fourcameras.html
>
> It means that the actual sharpness available with a well-tued Rollei TLR at
> f/8 is above 90 cy/mm, i.e. you could even choose a circle of least
> confusion of about 10 microns for you depth-of-field tables !
>
> Moreover as far as the Rollei TLR is concerned, correct me if I'm wrong but
> I think that there is no special position of the film pressure plate for 220
> rollfilm ; it means that without its backing paper, 220 film is "floating"
> between the plate and the film gate, with a spacing designed for 120 (film +
> paper) thinckness... except for Rolleis with the glass pressure plate. (this
> is anotther story..)
>
> all the best !
> --
> Emmanuel
>
>
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