[Leica] Flange measurements

["Dante A. Stella" <dante@umich.edu>]

Gentlemen:

Interestingly, when I was supposed to be  getting ready for another day
of work, I called Konica in New Jersey to grill them about flange
distances.  After some audible page flipping, I was presented with the
same 28.00 +/- 0.03mm figure Erwin got.  I also got some interesting
tidbits regarding repairs:

    1.    Konica USA expects any errors with Leica lenses to manifest
themselves in the rangefinder, not in actual focus.  This is "by the
book."  Erwin seemed to say that the German facility thought it would be
actual focus.  That is a distinction between "focus" and "focusing."

    2.    Measurements are made using a special device supplied by
Konica Japan (hmm...) and are made from all four corners to the film
plane (not clear how that is defined).  It may be impossible to
duplicate the 28.00 measurement with anything else.  Makes me want to
send them my M3 for measurement on the same apparatus.

    3.    The Hexar body has eight adjustment points (4 in the lens
flange and 4 behind the film plane).  All eight have alignment thrust
washers installed when the camera is shipped.  This is, per John Van
Stelten, how LTM cameras addressed this issue.

    4.    The adjustment planes can be aligned, by virtue of the washer
sizes, down to 0.01mm.  They did not indicate whether they actually did
this.  On the M, the adjustment is behind the shutter.

    5.    Alignment of the film plane necessarily follows any change of
the shutter.

    6.    The RF mechanism is aligned for linearity from infinity to 1
meter.  This is the minimum distance without creating parallax problems
in RF adjustment, or so they say.

    Then later today, someone sent me an email message indicating that
he measured his Hexar (with something called a depth gauge) to be
0.008mm from 27.80mm.  Putting two and two together, I would then wonder
if

    1.    Konica's measuring device is somehow different; or

    2.    That different people may be measuring different ways.  The
Hexar has two film rails, in part because it has no sprocket wheel (it
uses some kind of optical sensing to determine frame spacing).  The film
travels between the outer rails.  The pressure plate rests on both the
back of the film and the outer rails.  The outer rails are about a
film-thickness difference from the other (inner, on which the film
rests).  Film thickness is... 0.13mm (for TMX135).  28.00-0.13 (or more)
= 27.87.  If that clearance between the rails is indeed 0.2mm (to
account for thicker film)... you end up with the magic 27.80.

If I recall (my M3 has film in it), it only has one set of film rails,
what would be the inner.  I assume that this is where the 27.80mm is
measured.

Maybe it's better to just shoot pictures with it.

Cheers
Dante