Archived posting to the Leica Users Group, 2000/03/19

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Subject: Re: [Leica] Film flatness
From: Jerald Rosenfeld <>
Date: Sun, 19 Mar 2000 11:51:32 -0800

IF I am not mistaken Linhof or SInar offer vacuum 4x5 film holder. If
you think LEica lenses are expensive these filmholders are outrageous.

Mike Johnston wrote:
> There is a 35mm camera (the Contax RTS III) with a vacuum back designed
> specifically to keep the film flat. There either is, or will be, a
> medium-format camera that has a vacuum back to keep the film flat (one
> is promised for the Contax 645, which is selling like hotcakes BTW,
> and--much to Contax's surprise--doing better in the USA than in home
> market [which for Contax is Japan]). I don't know whether this is
> actually available yet and I'm too lazy to go check.
> Film flatness is indeed a valid technical concern for specialist
> photographers. It's just not of much practical concern to photographers
> for pictorial photography--except sometimes when a frame with a "memory"
> of a "set" curl creates obvious unsharpness in a negative--and sometimes
> in large format. Which is why you don't see much effort to correct the
> "problem" in the products on offer (Contax excepted, and I have a
> feeling this has something to do with the fact that Kornelius Fleischer,
> head of 35mm optics at Zeiss, is an aficionado of high-resolution
> photography! He uses surveying tripods and has access to the legendary
> Zeiss S-Planar process lenses for enlarging, lucky dog!)
> The Contax vacuum backs were based on the technology used for 10x10
> aerial reconnaissance and satellite photography.
> You think medium format is bad, try large format. It's been demonstrated
> that the film not only does not lie flat, it can _move_ during
> exposures. This can occur because of "sagging" or because of the film
> suddenly being exposed to ambient humidity when the darkslide is pulled.
> At any rate, measured with a micrometer, 4x5 film lies very far from
> flat in a holder. In fact it resembles a rumply blanket.
> At least one of our contributors uses a special vacuum 4x5 back, and
> another has devised a system whereby he uses five little patches of
> double-stick tape on the inside of his 4x5 holder--he carefully loads
> the film and then presses it lightly with his fingertips to make the
> tape "engage" with the base side of the film. He then uses these holders
> for very long exposures, so his film won't move or sag during the
> exposure.
> --Mike