Archived posting to the Leica Users Group, 2004/03/09

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Subject: [Leica] Diopters, contact lenses, and aging eyes
From: Peter Klein <pklein@2alpha.net>
Date: Tue, 9 Mar 2004 14:08:11 -0800 (PST)

I have an interesting problem with my viewfinders not appearing in focus.
I've noticed it in two instances: 

1. When I use my .76x M Leicas with the 1.25x magnifier (nearly 1:1)
2. When I use a Zorki 4 RF (which has a 1:1 viewfinder).

I'm nearsighted. I wear either contacts or bifocal glasses. My contacts
are monovision, which means they are set for distance vision in the right
eye (with a bit of astigmatism correction), and for reading in the left
eye. I sight through the camera with my the right (distance) eye.

When I'm shooting concerts with my M6TTL and a 90, I can focus fine with
my right (distance) eye and no magnifier.  But if I add the 1.25x
magnifier for additional security, I find that the scene looks to be in
better focus with my left (reading) eye.  I found a similar pattern when
using my bifocal glasses.  With no magnifier, the image was clearer using
my distance lens.  Add the magnifier, and I could focus more easily if I
used my reading lens.

Note that I'm not talking about rangefinder alignment here, just the
clarity of the image through the viewfinder.  My perception of it may be
confused by occasional contact lens shifting. All of the above is less
noticeable in bright outdoor light.

Case #2 is the same issue with a different camera.  I recently inherited a
Zorki 4 Russian rangefinder, vintage 1962, with Jupiter-8 50/2.  It just
returned from a trip to Russia, where it got a CLA from Oleg (thanks,
Karen!).

The Zorki has a nice 1:1 combined range/viewfinder with a diopter
adjustment concentric with the rewind knob.  It's similar to the RF focus
adjustment on many LTM cameras.  And here's where I'm having trouble
similar to the M6-plus-magnifier situation I described above.

For some reason, I can't get the viewfinder's diopter adjustment set
exactly right when I have my contacts in. It goes in and out of focus
around a certain point in the lever's travel, but it's usually never quite
right, always a little fuzzy.  And then once in a while I get it
perfectly. (Contact lens shifting?  Something inconsistent in the camera?)

Oddly, I don't believe I have this problem when I take my contacts out and
use the camera with no glasses or contacts at all.  I have to set the
diopter adjustment differently, but it focuses more clearly.

Can anyone give me some tips on what's going on, and how to best cope with
it?  (Apart from the fact that Peter Is Now 50 And Has To Accept It).
Advice from optometrists especially welcome.

Thanks,
- --Peter Klein
Seattle

P.S. I just shot a few test shots with the Zorki, which look OK. I am
actually finding that I like the camera.  In some respects, it's a more
convenient shooter than my old IIIf was (please do not stone the infidel
:-).  It feels sort of like a cross betweena IIIf, an M3, and a piece of
Soviet industrial machinery.  More later.



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