Hi all OM1'ers,
In replay to a question on his exposure tests
Gary Reese reported the following errors (in stops) while using an
MR9 silver oxide battery adapter on 4 different OM1's:
For 1/25th @ f/11 I got the following errors (in stops) from the four cameras:
-1/3, +1/3, no error, +1/3 (approx EV11-12)
Then at 1/25th @ f/5.6: (approx EV9-10)
+1/3, +1 1/3, +1/3, +1
Then at 1/25th @ f/2.8:
+2/3, +2 2/3, +2/3, +1 1/3 (approx EV7-8)
Comment:
Note these errors were against an exposure tester not
comparing a silver oxide +MR9 adapter
against the same camera with a Mercury battery.
==================================
Gary,
Given That the errors go down with increasing EV in your test
and the expected errors from MR9 should increase with increasing
EV I would guess the MR9 is a small part of the exposure error
and your camera's need calibration. This is particularly likely given
the large magnitude of error at modest EV.
One further point when doing tests like this :
If there is a very bright light behind you shining into the eyepiece
as you balance the meter and the tester is setting a low EV value,
then stray light into the eyepiece can cause significant errors.
You can sanity check for this by moving your eye closer or further from
the eyepiece or varying the shading and watching the meter.
In the real world this is seldom a problem except maybe microscopy or
if you are unlucky with direct sun from behind with a dimly lit subject
like a slot canyon.
From a stability point of view the the silicon photocells of the
later OM models should theoretically never need calibration
although other components can cause some drift and contamination
can cause leakage paths.
Tim Hughes,
Hi100@xxxxxxx
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