[Leica] Re: Konica facts

[Henning Wulff <henningw@archiphoto.com>]

>Erwin P., thank you very much for setting the record straight on the 
>Konica-Leica
>compatibility question. This explains the somewhat odd experiences 
>many of us have
>had.
>
>It is true my Hexar RF was used mostly with the 21mm lens,susually 
>stopped down to
>about f5.6, therefore masking any obvious focus problems. I think 
>many other Hexar RF
>users mount the 24mm lens on it or other wide angle.
>
>But it is worth noting that not all Leicas have ideal flange-film 
>distances either. A
>recent inspection of one of my cameras, an M4, also showed 
>significant deviation from
>the correct distance. It seems this important measurement is not 
>undertaken by all
>repair technicians.
>
>Is it possible that the problem in most Hexar RF bodies may be easy 
>to fix with a
>slight amount of machining or shimming, as the case may be?
>
>Emanuel Lowi
>Montreal

Since we're talking about depth of focus rather than depth of field, 
the f-stop is important but not the focal length.

I just looked at some negs I had shot a while ago with all my cameras 
to check for focussing accuracy, and while the closer stuff is all OK 
and within tolerances for the stuff I'll be doing, most of the 
infinity shots with the Hexar seem to be focussed not on infinity, 
but closer. With the 50's it seems be at about 100m or more. This 
translates into a flange to to film increase of 0.025mm, a lot less 
than the 0.2mm that Erwin was told. I'll check it some more, but 
while my Hexar's flange to film distance does seem to be greater than 
my Leicas', it seems to be within an acceptable range for me.

I did the above checks with 135, 90, 75, 50 and 35mm lenses. If there 
is a serious problem with the flange to film distance, it should have 
shown up most strongly with the 35/1.4, as 0.2mm discrepancy 
translates to about a focussed distance of 6.2m when the lens should 
be focussed on infinity. Since I took these shots at full aperture, a 
serious discrepancy should have been obvious. Even using the rather 
generous DOF scales on the lens, it would have taken f/5.6 to bring 
things into acceptable focus. But, as I said, I am going to set up 
something to test this properly.

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    *            Henning J. Wulff
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