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From: dollas@uiucdcsb.CS.UIUC.EDU
Newsgroups: net.rec.photo
Subject: Re: Zooming during an exposure.
Message-ID: <11500013@uiucdcsb>
Date: Tue, 11-Mar-86 22:25:00 EST
Article-I.D.: uiucdcsb.11500013
Posted: Tue Mar 11 22:25:00 1986
Date-Received: Fri, 14-Mar-86 05:16:33 EST
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Nf-From: uiucdcsb.CS.UIUC.EDU!dollas    Mar 11 21:25:00 1986


   Different cameras use different schemes (eg Olympus uses off-the-film
metering, in which case the overall exposure would be adjusted, think of
it as an integration of light over time); I suggest that you experiment.
The simplest thing to do is the following: when the camera does not have
any film set the ASA to the lowest value, and take three 'fake' exposures:
one with max. focal length one with minimum and one with varying focal length.
The exposure time for a normally lit subject should be easy to monitor. 
Repeat the experiment in order to get some statistical significance (read:
peace of mind that you did it right). As you may guess, the inference can 
easily be made from interpolation of the time exposures!
   As a final word, you may have to place in the inside of your camera 
an 18% gray paper (this depends on where the light meter is located) in
order to get realistic exposure times.
   Good luck!

   Apostolos Dollas
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