Archived posting to the Leica Users Group, 2001/06/07

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Subject: Re: [Leica] Re: Hexar Back focus
From: Dennis Painter <dennis@hale-pohaku.com>
Date: Thu, 07 Jun 2001 07:42:45 -0700
References: <Pine.SOL.4.33.0106061619360.4174-100000@frogger.gpcc.itd.umich.edu> <3B1EB597.610639B@fuse.net>

This is the way it is on ALL M cameras. Good explaination Marshall.
Dennis

Marshall Hunt wrote:

> My Ms (M3, M4-P) have 4 rails.  The pressure plate rests on
> the outer rails, and the film travels over the inner rails.
> The film travels through a space defined by the outer rails
> longitudinally, and the difference in height between the
> inner and outer rails, vertically.  The emulsion side does
> not touch anything in the picture area, and the shiny side
> barely touches the pressure plate. (On my cameras you can
> see the abrasion where the plate touches the outer rail, but
> no abrasion in the center of the plate from the film).The
> pressure plate does not depend upon the film for support.
> Even my Zorki has 4 rails. Did Leica remove them for the M6?
> I doubt it. Hunt.
>
> Dante Stella wrote:
> >
> > The pressure plate is not flexible.  It rests on the film, which rests on
> > the inner guide rails.  When there is no film, it rests on the outer guide
> > rails (which are slightly raised).  This is pretty conventional with
> > modern motorized SLRs, at least as far as I can tell.  Too much force
> > against the film would be hard on the motors, I think.
> >
> > My M3 has no outer rails, and the plate rests on the film plane rails with
> > no film in it.
> >
> > On Wed, 6 Jun 2001, Mark Rabiner wrote:
> >
> > > John Collier wrote:
> > > >
> > > > I can only speculate but perhaps the flange to film distances are the same.
> > > > The difference may be in the measuring technique. If Hexar measures from the
> > > > bayonet flange to the pressure plate, this would give a greater distance
> > > > than Leica's  nominal 27.8mm which is to the front surface of the film.
> > > >
> > > > John Collier
> > > >
> > > ><snip>

In reply to: Message from Dante Stella <dante@umich.edu> (Re: [Leica] Re: Hexar Back focus)
Message from Marshall Hunt <huntmc2@fuse.net> (Re: [Leica] Re: Hexar Back focus)