Re: [Leica] Focusing at infinity

[John Collier <jbcollier@home.com>]

Sorry for the hastily written reply. There is only one cam! That cam is
coupled by a compensating mechanism to the focussing mount in which the
optical unit of your 135mm lens sits in. The compensating mechanism changes
the large movement of the optical unit, during focussing, into a shorter
movement that is compatible with the cameras rangefinder. The rangefinder in
the camera is matched to the range of focussing movement of a 50mm lens.
Lenses shorter than 50mm require a mechanism to increase the lens cam
movement as compared to the actual optical unit movement; while lenses
longer than 50mm, decrease the lens cam movement as compared to the movement
of the optical unit. The best description is in the hideously expensive book
by Gunter Osterloh, "Leica M, the advanced school of photography." If I am
still not being clear, please contact me off-list and I will try again.

Apologetically yours

John Collier

> From: "Dale R. Reed" <dale-reed@worldnet.att.net>
> 
>> Your M6 rangefinders probably are correct but the rangefinder cam on the
>> suspect lens needs adjusting.
> 
> I estimate that the lens focusing stop(if there is such a stop) must be
> moved about the width of half the infinity symbol.  Which will only make a
> difference when the lens is wide open at 3.4 and possible some difference at
> 5.6.   In other words this stop is keeping the lens from adjusting short
> enough to photograph an object at infinity.  Just a theory of mine.
> 
>> The lens rangefinder coupling cam is not the
>> lens focussing cam though they are linked of course.
> 
> I see only one cam John.
> 
> Do any of you LUGers know where(preferably in cyberspace) there is a good
> explanation of how the focusing system works on a M6?  Something more than
> what is in the Leica literature and Bower's books.   Thanks for the help.
> Dale
> ---
> $ dale-reed@worldnet.att.net    Seattle, Washington USA $
> 
>