Clint:
Thanks for the detailed info. I have a very complete shop and many many
tools.
However, after reading your note I hope that I am intelligent enough to
pass on doing my own calibration ;-)
Norm
----- Original Message -----
From: <clintonr@xxxxxxxxxxxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Wednesday, March 27, 2002 11:19 PM
Subject: Re: [OM] Calibrating an OM2n
> Norm Nadel wrote:
> >
> > How difficult is it to calibrate the OM-2n ?
>
> It's easy -- after the first 100-200 or so! ;^)
>
> Actually, to do the job properly requires some test equipment -- a
> shutter speed tester, a calibrated light source, and an exposure
> tester. You'll need to remove the top cover, the cover below the
> mirror, and replace the bottom cover with one that's been cut off at the
> MD opening just to hold the batteries in place.
>
> First, assuming all the mechanical functions are OK, you've got to set
> the curtains so they travel across the focal aperture at the correct
> speed. If they don't move at the proper speed, none of the other
> adjustments are going to do any good. And if one curtain is faster than
> the other, one side of the photo will get more light than the other --
> not a good thing!
>
> Once that's done, you'll need to adjust the high speeds by changing the
> position of the trigger switch -- that's what tells the camera's timing
> circuit that the shutter has begun to open. There's an eccentric for
> that, but hardly anybody uses it -- we just make minute bends to the
> contacts or the frame that holds them.
>
> Occasionally you run into difficulties with what Olympus calls the "Auto
> Limiter" -- a mechanical device that limits the highest speed the camera
> will deliver. If it's off, that can make the high speeds very difficult
> to adjust.
>
> Then adjust the lower speeds, primarily checking 1/8th second. There's
> a VR on the main circuit for that. Then you'll want to re-check the
> high speeds again, of course.
>
> Once the manual speeds are in tolerance, you can check the actual
> exposure at the film plane. This requires a special sensor that has the
> same reflectance as film so that the camera's sensors will operate
> correctly. This adjustment is also located on the main circuit. You'll
> want to check several light levels and set the camera for optimal
> performance throughout the range -- a little high at bright light, a
> little low at low light, dead on at mid-range, for example.
>
> Last, and functionally least, check and adjust the meter itself. Since
> the meter needle is an indicator only, it doesn't actually "control" any
> function. You'll want to check it for accuracy with a known-standard
> lens, on a calibrated light source, at several light levels. And don't
> forget that light entering the eyepiece will affect the needle's
> reading, too. If the meter's error is linear, the adjustment is by
> turning an eccentric on the ASA cam's follower. If the error isn't
> linear, you've got trouble -- that won't happen unless something's
> really wrong!
>
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