[Leica] Hexar RF compatibility - one observation

[Holger Merlitz <merlitz@int.fzk.de>]

Dear LUGers,

My name is Holger Merlitz and since a couple of months I have been a
"passive member" of LUG, just following the discussions as presented in
the archives. There was a Konica Hexar RF - Leica M compatibility thread

coming up several times and I think I should share one observation which

I have made recently when using the 90mm F2.8 Hexanon on my Leica M2:

When focusing on a far distant object, I am not able to bring both
images
in the focusing window on top of each other. The lens, set on
'infinity', just
remains slightly hyperfocal according to the rangefinder. This is not a
consequence of any rangefinder misalignment, as I have checked with my
other lenses (including Leica as well as Cosina/Voigtlander), which
perfectly
match the same object on 'infinity'. It is only the Hexanon displaying
such a mismatch, which is small: I estimate it to amount to 1/4 of the
width
of the 90mm framelines in my viewfinder. Under usual conditions it is
practically
invisible, but during my trip to Hong Kong, where you have those huge
neon letters
on top of far distant skyscrapers, it was clearly discernible, as well
as the
fact that my other lenses do perfectly match.

I think the fact that I can't focus an object at infinity may indicate
that
the lens is designed to fit to a camera body with a larger lens-to-film
distance, is this correct? This would be in agreement with the claim
that the
Hexar RF body is actually 28.00 mm deep instead of 27.80 as the Leica M.

Of course I don't know whether the observed deviation of 1/4 frameline
width
corresponds to 0.2 mm lens-to-film distance. Does any of you LUGers have
a clue?

Does it have any effects on the image quality? Not that I have observed
any. My
images are nicely sharp, not only at infinity but at all distances. No
wonder
since the deviation of 1/4 frameline width is certainly well covered
within the
DOF of the F2.8 lens. But things may be different when using a Noctilux
or the
75mm F1.4 on the Hexar body. As far as my 90mm Hexanon is concerned,
I am very
much satisfied with the performance of the lens and I do not worry about
any
potential tiny incompatibility.

With regards,
Holger Merlitz,
Karlsruhe

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