At 01:56 PM 2/22/2003 -0800, you wrote:
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
I think my decision to shoot Velvia at a speed other than the
manufacturer's recommendation implies that I take the 1/3 stop
seriously. I think I meter fairly carefully, but I like brackets for the
information returned and for "insurance." I've actually had to shoot quite
a lot of Velvia before really getting to know its characteristics and the
effect of that 1/3 stop. It is a small increment. I don't mean to suggest
it is insignificant.
Joel W.
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