Hi Rich:
<< Well, <expletive deleted>! Now I remember your saying that, Gary.
Every exposure I made yesterday was focused to where the shimmer just
disappeared... Guess I'll have to go out and shoot a test roll, and take
copious notes, cause I wanna KNOW for sure. >>
I'd recommend that for anyone. Be sure to try with and without a filter,
too. :-) The difference between shimmer and just past it is
approximately a 50ss of resolution.
<< Is it possible that it differs from body to body, with minor
differences in lens mount-to-film plane distance? Would probably have
to be a MAJOR (out of tolerance) variation to have a noticeable effect,
eh? >>
The manufacturing tolerances needed to accurately focus 50mm f/1.4 and
f/1.2 optics are very tight. But when I say the film eveness is the
ringer in all this, I mean the bend in film from one frame to another
can be detected with a vertical autocollimator - which begs the question
of: "what even is the perfect film to flange distance to use on a test
bench?" (I know there are specs on this, but an autocollimator won't
reflect off a black pressure plate). When I first saw the differences
between frames, I could appreciate why Contax marketed a ceramic vacuum
back. A practical solution to this is to stay away from such apertures
and just use faster film. It might very well increase the odds of a
keeper. Then we can right-brain our way to photographic bliss, rather
than fret over something that keeps Leicaphiles anxious. Of course,
film bend has no bearing on focusing accuracy, but its just one variable
in a long string of manufacturing tolerances that makes a fine picture
an amazing feat.
I bet that plastic autofocusing SLR's with f/3.5 and slower optics are
being built to lesser manufacturing tolerances than OM's! Bayonet and
pray if you use a 50mm f/1.8 on a Canon Rebel G.
Comments from technicians much more experienced than I are welcome . . .
Gary Reese
Las Vegas, NV
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|