Archived posting to the Leica Users Group, 2002/01/13

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Subject: [Leica] Re:Hexar Leica Bayonet Mount to Pressure Plate Distance
From: Howard Cummer <cummer@netvigator.com>
Date: Mon, 14 Jan 2002 05:34:13 +0800

>Date: Sun, 13 Jan 2002 14:11:25 +0100
>From: Holger Merlitz <merlitz@int.fzk.de>
>Subject: [Leica] Hexar RF compatibility - one observation
>I think the fact that I can't focus an object at infinity may indicate
>that
>the lens is designed to fit to a camera body with a larger lens-to-film
>distance, is this correct? This would be in agreement with the claim
>that the
>Hexar RF body is actually 28.00 mm deep instead of 27.80 as the Leica M.
Holger,
The Hexar back focus is 28.00mm with a tolerance of +/- 0.03mm. By Back 
focus is meant the distance from the bayonet mount to the metal pressure 
plate in the film chamber without film. The same distance for Leica is 
27.95 (+/- 0.02mm) without film and 27.8 estimated with film. The latter 
number is quoted in lots of literature about Leica and has been the root 
cause of lots of misuderstanding about back focus incompatibility between 
Leica lenses and Hexar bodies. You are doing the reverse, fitting a Hexar 
lens on a Leica body, and could be caught in a combination of tolerances 
working to reduce the focus point on the film plane. However, since you 
can't see any problem then you don't have one and can enjoy going out and 
taking pictures. :)
Best Regards
Howard Cummer.

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