Archived posting to the Leica Users Group, 2000/07/26

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Subject: Re: [Leica] Peeling R4 Bayonet
From: Doug Herr <telyt560@cswebmail.com>
Date: 26 Jul 2000 14:57:54 -0700

On Wed, 26 July 2000, CapsTeeth@aol.com wrote:

> 
> In a message dated 7/26/00 1:31:12 PM Eastern Daylight Time, 
> sdmp007@pressroom.com writes:
> 
> << CapsTeeth,
>      Changing the bayonet mount yourself withOUT having the proper
>  calibration tools is foolish. The flange distances are critical for sharp
>  focus. >>
> 
> I've never changed an R lensmount, but I've done several Nikons and Leica M's 
> and the mounts fit flush with the body casings with and the screws tighten 
> into their threads until they are tight, just like rear lensmounts.  There 
> aren't any provisions for "calibration".  I checked with Fargo Enterprises 
> and they didn't seem to know what a "lens mount calibration tool" was.  
> Perhaps Leica R cameras are different. 

I haven't changed lens mounts, but I've removed and replaced 'em when

) replacing broken plastic lens release tabs on SL bodies
) replacing the main casting of a broken R4sP

and on neither camera were there any calibration adjustments.  This issue is more important with an M than with an SLR because with the SLR, whatever's in focus in the viewfinder (assuming correct mirror & viewscreen alignment) will be in focus at the film plane.

The only "calibration" problems I've heard of are on FD-series Canons.  The lens mount was positioned at the proper distance from the film plane at the factory with shims between the mirror box casting and the flange; a good whack could shift the shims enough that the plane of focus was no longer parallel to the film.  This is all in the cobwebbed corners of my memory; can anyone confirm this?  My SL and R4sP seem to have been made precisely enough that shims are not nessesary.

Doug Herr
Sacramento
http://ourworld.compuserve.com/homepages/telyt
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