OM Viewfinder Diopter Puzzle

pagpow

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Jul 26, 2007
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Puzzle – I am generally near sighted, with a small amount of astigmatism. I use standard eyepiece diopters (no correction for astigmatism) on my cameras for focusing. After reading what’s on the web, I experimented with various options -- with great success. That has not transferred to OLy OMs.

On Leicas, I use a –3.
On Canon FD, I use +3.
On Xpan, I use –4 (no –3 was available).

So when I learned that Nikon diopters fit the Oly OM line (thanks, Ruben, Pickett Wilson, and RFF) I ordered a +3 and a +2 (just to be safe, given the different native correction of Canon FD (-1.2) and Oly OM (-0.5 or –2.0 depending on which source you believe)). Neither works.

It is not that they are insufficient; they provide no improvement at all and make the view strange, like when I mounted a –3.0 on my Canon. I see to focus the Oly OM fine with my distance glasses on my eye, suggesting something within 0.5 and even 1.0 of my distance prescription should work, just as it does on the Canon FD. But it does not.

Thoughts?
 
OM bodies have a minus 0.5 built into the eyepiece glass. Adding a minus 3 equals -3.5. An Olympus brand diopter marked -3 is actually -2.5, combined with the eyepiece equals -3. What is the Nikon eyepiece equal to by itself? This must be figured in to know what a Nikon diopter power really is. But why you see strange or it doesn't make any difference, I don't know. John
 
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