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Re: [OM] which meters correct?

Subject: Re: [OM] which meters correct?
From: clintonr@xxxxxxxxxxxxxxxx
Date: Thu, 28 Mar 2002 17:30:33 -0600
This is a bit unusual, but not impossible.  The ANSI tolerance for the meter
reading is +/- 1/3 stop, so if one camera happens to be at the extreme one way
and the other at the extreme the other....

Of course, one might be "perfect", the other out of tolerance.  Or they may
both be off, one worse than the other!  The only way to test is to use a
calibrated light source.  (BTW, when we say "calibrated light source", that
means not only that it's been checked, but that it's power supply is built to
provide a constant light output regardless of the input voltage.)

Whenever people ask about this sort of problem, we tell them the only way to
"match" cameras is to send them all in at once so we can put them on the
testers one after the other and adjust the meters as closely to each other as
possible.  If they come in at different times, there's a chance that, since
they are within tolerance, the tech might not see the need to "tweak" the
adjustment.  Even so, when we "match" cameras, there's sure to be some
deviation throughout the range of ASA/ISO's, speeds, apertures and light levels
-- no two cameras are ever _exactly_ alike!


Charles Sdunek wrote:

> Well folks, lets have some input and advice....
>
> While out yesterday shooting a particular scene for our current tope event,
> I realized I have a problem.  Is it a big one?  Probably not, but still
> troubling.
>
> I had my OM2n set up on tripod with my trusty 85/2 and was happily
> bracketing a few shots of an interesting scene when I decided, "hey, I'd
> like to get a few of these in B&W too. So I grabbed my trusty OM2 out of my
> bag and attached it to the tripod with the same lens at the same aperature
> focused on the same spot and found that meter was reading 2/3 of a stop
> higher.....ACKKKK  I was horrified!  I ran the series of shots again with
> that camera, figuring that if I bracketed the same way, at least one of the
> shots would be correct.   Then I went back to my truck.  I took out my gray
> blanket lined carhartt jacket and opened it up using the lining as a
> uniform place to take light readings and what do you know,  with the film
> speed set at 100 and the lens at f5.6 and both cameras in AP mode, one
> suggested a shutter speed of 30 and one of almost 60.  Using the
> compensation dial, I verified that there was indeed 2/3 of a stop
> difference between the two.
>
> So, how do I know which is correct?  It would be easy enough to compensate
> for this if I knew which was the bugger (or if both are off).  This only
> needs to be temporary because as soon as I have a little extra cash, I am
> going to send the OM2 in for CLA.  At this point I will know which camera
> is correct.  IF the om2 was corect then the 2n will be following it to be
> serviced shortly after.  If the 2n is correct, then the 2 will have been
> adjusted.  but until that, how do I make do when I have no other trusted
> meter to compare them to?
>
> Charles
>
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