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Re: [OM] Auto Exposure Times & The Ideal Meteor Catcher

Subject: Re: [OM] Auto Exposure Times & The Ideal Meteor Catcher
From: HI100@xxxxxxx
Date: Wed, 24 Mar 1999 02:41:05 EST
In a message dated 3/23/99 5:33:05 AM Pacific Standard Time,
Wayne.Harridge@xxxxxxxxxxx writes:

<< The thing to keep in mind is that even though it gives you a long exposure
 there is no guarantee of the accuracy.  My guess is that with very low light
 levels, leakage currents within the exposure/timing circuit probably have a
 major contribution in determining the actual length of the exposure.
 Perhaps the "spec" is the longest exposure for which the exposure/timing
 circuits are reasonably accurate. >>

I seem to remember that at least for the late model OM2 and OM2n they limited
the exposure time to conserve batteries from being discharged with excessive
exposure time by lighting an LED to provide controlled "leakage" to the
photodiode detector. I remember my early OM2 (in it's case) with lens cap on
could discharge the batteries if set off accidently. (Without the case I seem
to remember some light leakage through the eyepiece reduced exposure time in
bright ambient light. )

Thus, if you can find the limit LED maybe you could paint it over/cover it in
the OM2 and get much longer exposures? In any case the early OM2 may provide
significantly longer exposures but you would probably want to use an external
battery to avoid battery problems. (Some of the web based sites have suggested
kludges to run the camera off external power).

I checked the schematic of the OM2S and could not see any easily identifiable
exposure limit LED.

Tim Hughes 
hi100@xxxxxxx

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