Archived posting to the Leica Users Group, 1996/12/13

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Subject: Re: Leica-Users List Digest V1 #294
From: Jim Bielecki <jbieleck@northland.lib.mi.us>
Date: Fri, 13 Dec 1996 04:40:39 -0800

> I have a question about an obscure lens mount adapter.  It's a "Canon
> Lens Mount Converter A".  The store claims it's a converter from Canon
> FD mount to Leica thread mount.  If I were sure that this were true I
> would buy it.
> 
> I worry that the store may be mistaken, however.  I have a piece of
> documentation, namely Viewfinder (LHSA magazine) Vol. 28, No. 2, 2nd
> quarter 1995, p. 35, showing a "Canon Lens Mount Converter B," which
> is supposed to adapt any breech bayonet Canon lens to Leica thread
> mount.  Now, my understanding was that the difference between breech
> bayonet and FD mounts was in the presence of an aperture coupling pin
> (not important for a rangefinder) and the presence of a locking ring
> on the lens (not the mount), but that the two systems are otherwise
> interoperable.  So why would there be two different "Canon Lens Mount
> Converters" then?

I have in front of me Carl Shipman's "How to Select and Use Canon SLR
Cameras" published in 1977.  On p. 85 it states, "Screw-type extension
tubes require adapters on both ends to fit breech-lock mounts on Canon
SLR lenses and camera bodies.  Lens mount converter A fits on the camera
body and accepts screw-in extension tubes, or even a screw mount lens
from the rangefinder lens assortment.  This converter itself adds 2.8mm
of extension.  At the front end of screw-type extension tubes, use lens
mount converter B to accept Canon FD and FL-style lenses".