I nominate Paul's empirical method as possible side bar material for the
focusing section of the OM-Book. It provides some interesting insight
into the optics of the focusing system and tells me immediately that if
I can't see well at two meters then I should have some optical
correction.
I see fairly well at two meters but not perfectly. I don't need
correction for normal activities but perhaps I do need correction for
critical focusing. I thought I was OK since I can see grain and dust in
the focusing screen without optical aid. However, looking at the
bookshelves two meters away, the text on the spines is readable but not
truly sharp.
Thanks Paul.
Chuck Norcutt
Woburn, Massachusetts, USA
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I measured the apparent distance of the focusing screen of an OM-1N as
follows:
I set the camera up facing a light surface with the lens way out of
focus. I
aligned another camera with a Tamron 90mm macro behind the eyepiece and
focused on the grain and surface specks of the screen. Then I read the
distance off the macro and subtracted the distance from the eyepiece to
the
second camera's film plane. (This was only a small correction.) I got
just a
bit over 2m, less the 10cm, so the apparent distance is, as far as I can
tell, very close to 2m. This is in line with my own dioptric correction
needs. I am slightly nearsighted past about 1m, and I use the least
negative
diopter.
Paul Farrar
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