At 21:39 8/8/01, Winsor Crosby wrote:
I do not think that is really true. It would be true if the eyepiece
worked like a telescope or microscope, i.e., without a screen. The lens
projects an image on the screen. Your eye then evaluates the sharpness of
the image. Even if your eye needs correction you can focus the camera
accurately if you can see a sharp image on the screen.
--
Winsor Crosby
Theoretically you're right. The problem I had prior to installing dioptric
correction was a slightly mushy image on the focus screen, even when it was
in focus, which is easily confused with slightly out of focus. I would
have to turn the focus ring back and forth to find "center" and use the
split image if possible. This was even more a problem in low light levels,
even with very fast lenses.
With dioptric correction, focus "snaps" into place, particularly with the
faster and longer lenses, without the ambiguity and in lower light
levels. A high level of sharpness possible in the viewfinder makes it much
easier to tell when it is and isn't in focus. My focusing became much,
much faster and noticeably more accurate.
With care it is possible to focus accurately with minor mypoia, hperopia or
presbyopia that slightly blurs the focus screen. I did it for a very long
time (slight myopia and moderate presbyopia). Correcting the viewfinder to
my vision made a huge difference though. Didn't know what I was missing
until I got the OM-4 and adjusted it. After that I got corrected eyecups
for the OM-1n and OM-2S.
BTW, I hated wearing glasses and trying to look through a viewfinder. It's
difficult see the viewfinder display, and to compose accurately.
-- John
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