On Saturday, February 22, 2003, at 05:40 AM, Joel Wilcox wrote:
This is not the "proper" way to test film speed for one's taste and
one's camera. The proper way to do it is to set up a well-lit,
balanced scene with perhaps a white shirt and a gray card in it and
then shoot brackets using the ASA dial to change exposure. But when I
did that, I didn't find anything wrong with the ASA 50 setting. In
the field, I seem to get slightly different results. I think 40 must
be a little more accurate, since many people complain about the lack
of shadow detail with Velvia. Even so, a 1/3 stop difference is very
small!
I think some would argue with that. The fact that your field results
are different also argues with that. What it does not take into account
is the different ways people meter a scene. In the past with the low
saturation/contrast films/low latitude films we dealt with many learned
to select what they knew to be average light areas and compared them to
readings for the highlights and made a judgment to maximize saturation
and minimize highlight blow out. Other people just point and let the
camera expose the scene. That is why testing, taking the kind of
pictures you normally take, is important. It is easier to set the ISO
than to complete adjust your metering technique. 40 may not be more
accurate as you found in your controlled test conditions, but for the
way you meter an ISO setting of 40 gives you the best results.
Winsor Crosby
Long Beach, California, USA
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