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Re: [OM] questions about other low ev cameras

Subject: Re: [OM] questions about other low ev cameras
From: HI100@xxxxxxx
Date: Mon, 3 Apr 2000 23:11:10 EDT
rtomcala@xxxxxxxxxxx writes:

<< With the release of
 the OM2n, they added a small led in the viewfinder that added to the
 exposure and limited the long exposures to about 2 minutes.  This is
 why, although I love my Om2n, I keep my OM2 also.  The OM2 may be hard
 on the batteries during long exposures, but it gets the shot ! 
>>
Rand,
           Both the OM2 and 2N have led limiters. Their operation actually 
causes exposure errors for very long exposures in both cameras but the errors 
only start after 2min in the 2N. And the maximum time does not go to a lot 
longer than 2min. The 2N exposure cycle only differs from the 2 in that an 
analog timer delays the on-set of when the led is switched on and also the 
led is brighter causing the limiter to act quickly once switched on. The 
brighter LED is also more reproduceable over temperature etc so the limiting 
action time has a much tighter tolerance and does not contribute errors below 
the 2min timer limit. On the other hand the OM2 led limiter forces the camera 
to act as if there is a fixed very low light in the scene over most of the 
exposure cycle instead switching in only after 2min. Since exposures are log 
light intensity related the OM2 errors introduced only become very 
significant when the led level and the scene light level are getting to be 
similar in magnitude. The OM2 more gradual limiting action does allow for 
significantly longer exposure times but the limiter does eventually add 
significant errors although by that time film reciprocity is probably a much 
bigger problem.

             >> Tim Hughes <<
             >> Hi100@xxxxxxx


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