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From: aipdc@castle.ed.ac.uk (Paul Crowley)
Newsgroups: comp.graphics
Subject: Re: HELP NEEDED IN PHOTGRAPHING SCREENS
Message-ID: <8130@castle.ed.ac.uk>
Date: 29 Jan 91 12:11:18 GMT
References: <1991Jan27.232910.22575@ms.uky.edu> <1991Jan28.010515.708@vixvax.mgi.com>
Organization: Edinburgh University Computing Service
Lines: 22

keeney@vixvax.mgi.com (Richard Keeney) sez in <1991Jan28.010515.708@vixvax.mgi.com>
>Then open the lens
>one stop for each time you double the exposure time.  For example, if the meter
>reading was f-16 at 1 second, you could properly expose at f-11 for 2 seconds,
>f-8 for 4 seconds, f-5.6 for 8 seconds, or f-4 for 16 seconds, etc.  The
>f-stops marked on most lenses follow the sequence: 
>
>.. f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22, f32, f44, f64 ...
>
>Descending from right to left one of these steps doubles the exposure (the
>numbers are proportional to the inverse of the diameter of the aperture,
>the exposure being proportial to the area of the aperture).

This guy seems to know exactly what he's doing, but he's made a slight
slip up there: he's right the second time, not the first.  If the
reading is f-4 for 1 second, you could expose at f-8 for 4 seconds, etc. 
I shall be using most of the advice he gave, since I'm making a film and
I shall be doing some computer animation.  (It will be brain-stompingly
low quality anyway, our camera is thirty years old.)

\/ o\ Paul Crowley aipdc@uk.ac.ed.castle
/\__/ Trust me, I know what I'm doing.