Archived posting to the Leica Users Group, 1996/04/11

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Subject: Re: M lens for 645 format
From: Gang Huang <>
Date: Thu, 11 Apr 96 18:30:40 EDT

I am also surprised to read that the lenses designed for 35mm have the
coverage of the 645. 200mm is believable, but 90mm has to be a stretch, and
I just 
unscrewed the optical unit off my 50mm DR, and tried. It didn't quite cover
6x4.5cm area, and I don't expect anything shorter than 50mm to have the
coverage either (except maybe the PC lens). Another problem with shorter
lenses is that they don't provide enough clearance for the mirror box.


Gang Huang
AT&T Bell Laboratories

At 06:43 PM 4/11/96 +0100, joe b. wrote:

>Unghhh prfft skrfffftttt!
>Once in a blue moon, I hear something that revises my understanding of
>the universe I inhabit.
>So, some questions. 
>(1) When you say you have these M lenses converted, what exactly do you
>have done to them? Can this be done by fitting M lenses into a custom
>made converter, or do the lenses actually have to be modified?
>(2) You refer to coverage on the negative. Is the coverage good enough
>to use slide film in this setup without vignetting? 
>(3) How do you select which lenses to do this with? What I mean is- do
>you select those particular focal lengths for any reason to do with
>compatibility with this format, or are they simply the focal lengths you
>would want to use anyay?
>Anticipating some slightly different medium format photography...
>joe b.