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Re: [OM] Help!

Subject: Re: [OM] Help!
From: Jim Couch <jamesbcouch@xxxxxxxxxxxxx>
Date: Wed, 19 Nov 2003 22:02:59 -0800
I am sure some other CAT lens users will chime in hear, but it is my recollection that mirror lenses do not transmit as much light as one would expect at a given aperture - some light is lost (due to the mirrors?) So your f/8 may in reality be f/11 or even worse as far as light transmission goes.

I have the same problem with an after market 200 f/2.8 it is about 2/3 of a stop slower than one would expect. When basing exposures on the TTL meter all is fine, but an external meter can be off if you don't compensate for the loss.

I think you will find your exposures are fine with TTL metering.

If your actual light transmission is more like on an f/11 or f/16 you may not get enough light with even the T32. With ASA 100 film at f/8 you should get about 13' it would be considerably less than this at f/11 or f/16. (probably less than 6 feet.)

Jim Couch

Douglas Tourtelot wrote:

I just got a Tam*on 500/8.  I am having trouble with expected exposures on
my OMs.  I have not sent anything to the lab, but something is not right
here.

For example, when I spot meter with my OM4 and my Sekonic 508, I get vastly
different readings (the OM4 reads 2-3 stops slower than the Sekonic).  Also,
with both the T-20 and the T-32, according to my OM2SP, I can't pump enough
light at 8 feet (ASA 100) to get the meter to read OK.  It always says
"UNDR".  This is in "AUTO" with the speed set at 1/60. Now the T-32 at 8
feet should melt the film<g>.

I believe that the A2 adapter is installed correctly (the tab is in the
notch) and this lens is supposed to be a f8 (T-stop of 9-something, but that
should not be causing all these woes).

What the heck am I doing wrong?

PS.  What a dumb lens for Seattle in the winter<g>.  Hand-holding at 1/2 is
not so easy with a 500mm lens!  And to think I actually bought ND2 and ND4
filters for it in case there was just too damned much light!!




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