From: Sil Horwitz (silh@earthlink.net)
Date: 04/25/00-10:09:32 AM Z
At 2000/04/25 07:32 AM -0700, you wrote:
>The there's the variablity of the sun itself. Montana sun in June is
>different
>from Montana sun in December which is still different than the sun that hits
>the ground in LA. any time of the year. So anybody's empirical tests will
>only
>be good for the surrounding area, will it not?
Though I realize we all consider ourselves as artists first, it is
technically possible to have meters to determine the amount of light (not
just the intensity) on a quantitative basis. It would even be possible to
pick out the light frequencies we wish to measure. Then the structure of
the light at any particular time in any particular place would be
irrelevant, as everything could be standardized. The advantage of the
artificial light source is that standardization (light source - not
materials!). And that's OK for commercial work or testing, but in my own
experience often the variations bring out qualities that are finer than
what was originally expected.
If I recall, the weather people (at least here in Florida) measure and can
provide the exact UV content at any particular time. Worth considering.
(Some of our TV stations give a "sunburn" number - 15 minutes without
protection in direct sun will burn - which might be transferable to an
exposure number!)
Sil Horwitz, FPSA
Technical Editor, PSA Journal
teched@psa-photo.org
silh@earthlink.net
Visit http://www.psa-photo.org/
Personal page: http://home.earthlink.net/~silh/
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