Re: Leica-Users List Digest V1 #649

[Jim Zietz <jzietz@unix1.sncc.lsu.edu>]

>> From: Edward Meyers <aghalide@panix.com>
>
>> My thoughts go to making photographs with lenses and that the lens
>> doesn't stand alone. It's has a camera to go along with it. So,
>> I lens should be tested with film on the camera, not on an optical
>> benchwhich gives you theoretical answers that are electonically
>> converted into make-believe prints.
>> One concern is the film channel of a camera. Bob Schwalberg noted
>> much about this to me during our many lunches in the big apple.
>> For example: The screw-mount Leica's film channel is not so good.
>> The M camera is much better. The old Nikon F was excellent.
>
>Solid point!
>
>In the process of sorting out the focusing problem in my M4-P I ended up
>doing the following experiment as well:
>
>Reload a strip of uniformly exposed film into the canister. Load it into
>the camera as ususal, advance a few frames and leave the shutter open at
>B. Remove the lens and look at the black film surface. In particular look
>at the reflection of a circular light from the film. It can be anything
>from oval to irregular and certainly varies from edge to center. And
>depending on whether you have film with stiff base or a thinner one you'll
>see different things. If you poke the film (with some blunt object) you'll
>get a feel of how much play there is between the film and the pressure
>plate at various parts of the frame.
>
>This should convince anyone that testing a lens separately is not
>sufficient if one wants to assess what the final image is like. And in
>particular things like the image flatness of Summicron 35 ASPH versus the
>non aspheric seem a bit of academic after this.
>
>
>
>Kari Eloranta

It is for these same reasons that I use enlargers with a piece of
anti-newton glass on top to hold the film flat. The Leitz enlargers (now
discontinued, I hear) are set up this way.

I don't know of a commercial lab that is willing to go to this trouble.

JZ