I have heard claims that there is no problem with the OM-4(T/Ti) etc. from
stray light in the viewfinder, owing to the location of the metering cells in
the baottom of the mirror compartment.
Today I tried out my OM-2SP (sorry to bore you!) with most of my lenses, and
I was walking back towards the house and it gave a little "beep!" - just one.
I thought "Hmmmmm...". I had my back to the sun, so did the camera. I then
deliberately pointed the camera so that the sun would hit the viewfinder. I
got several more 'beeps' for "overexposure". Setting the lens to smallest
iris aperture (f/16 or f/22 I can't remember) and re-trying, it didn't beep.
Setting the aperture back to f/8 or a lower f-number, it beeped again.
The OM-4Ti also beeped when the viewfinder was presented towards the sun. So
thet is 1/2000 at f/8 worth of light getting to the silicon cells, EV 17.
Presumably the light gets in through the pentaprism and past the
semi-silvered mirror into the photo cell. Of course, it isn't all black down
there because the shutter curtain might reflect a bit of this stray light to
the cell, depending on the taking angle of the little dewdrop-shaped lens in
front of it, or it might get to the lens on the photocell directly through
the mirror and get refracted by the dewdrop lens into the cell.
I used to suspect that this was possible, but I don't think I have ever
encountered it before.
Of course, this wouldn't be true for the OM-2 or OM-2n because of its fully
silvered mirror! So correct exposures with the old OM-2(n) look a bit more
secure in Auto mode.
Dave Bellamy.
http://hometown.aol.com/sitesearch/
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