Hi!
I just recently found out a thing that means a lot for me, as owner and lover
of several Carl Zeiss Jena screwmount lenses and user (lover <g>) of Pentax K
mount camera(s). I bought quite early the Adapter K, but found out that when
used with my M42 CZJ lenses, they would wobble (back and forth) and even could
be rotated in the K mount (affecting exposure!). I thought this was just bad
engineering of the original "adapter K", and stopped using M42 lenses via the
adapter (or had them permanently adapted to bayonet, like the 500mm mirror).
But lately, I found out that this sloppines was caused by different design of
rear flange of these CZJ lenses, different from Takumars!!!
(I don't have any M42 Taks so I didn't compare the CZJ and Pentax M42 lenses).
Basically, the Taks are all flat around the screw, while the CZJ lenses have
about a small ring area around the screw which is "higher" (0.2mm) than the
rest of the rear flange. Incidentally, the M42 > K adapter needs the lens to be
completely FLAT back to work properly!!!
Easy solution for those using the often excellent CZJ lenses (like a 20/2.8,
80/1.8, 35/2.4, and others) : cut out a ring 0.2mm thick (good material is e.g.
fibre B&W paper, singleweight). cut the ring such so when it's on the lens rear
flange, it covers the large recessed area and brings it level with the small
more central 0.2mm higher area (which is actually where the 45.46mm register
distance is measured from). Glue it in place with thin glue, or fix with tape,
whatever works...
You now have a lens adapted for use with Adaper K, and it will work as nicely
as any original M42 Pentax xxx-Takumar !!!
For some, this may be no news. But it certainly was for me :)
Frantisek
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