RE: [APML] Focusing the Mamiya and getting diff results

["Gene Horr" <genehorr@houston.rr.com>]

I've used the FM-60 on the focus screen for many years
with good results.  I've always wondered though how well
that screen is parfocal with the film plane.  On my
unit it appears to be good enough.  Perhaps you received
a unit just slightly out of the center spec?

I would test it by getting a caliper, and with the camera
on the refractor measuring the focal distance for each 
method.  Then starting a little further in than the 
smallest measurement bracket a series of images moving
through the focal points, writing down the measurement
each time.  This can be done from a light polluted 
location and the exposures only need to be 5 minutes 
long.  Then examine either a high-resolution scan or
the negs under a microscope to pick the best focal
point.  This will determine which method words best 
for your setup.

Gene Horr
genehorr@houston.rr.com

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