From: Carl Weese (cweese@earthlink.net)
Date: 04/26/00-05:38:44 AM Z
Sandy,
I checked into this during testing of ziatype POP materials a couple
years ago. Full sunlight literally was 'too fast' for good control with
many negatives. A three minute exposure is ok with a perfectly
repeatable artificial lightsource but too hair-trigger for hitting a
good inspection with variable sunlight. Moving to shade lengthened
exposures to the fifteen minute range which made it easy to nail a
'perfect' density since a variation of a minute or so was quite
insignificant. In the process I had wondered about sharpness
differences, but couldn't see any using a good (Great Basin) print
frame. Then I accidentally printed a negative emulsion side up with the
frame in shade: exposure was no different, but along with being reversed
in orientation, it was also quite unsharp. So then I tried the same in
direct sun and got a nice sharp print. Then I did it in sun *at a 45
degree angle* and got a _really_ unsharp print. Prints at 45 degrees to
the sun with the negative oriented properly were tack-sharp.
This limited experiment indicates that the difference in sharpness
resulting from point source vs diffuse light may be unimportant
providing negative-paper contact is sufficient. The biggest change I've
seen in technical quality of my large prints has come from switching
from a crummy spring-back frame to a NuArc vacuum frame which gives
wonderful crispness using my Edwards Engineering lightbox (highly
diffuse) as UV source.
---Carl
-- Website with online galleries and workshop information at: http://home.earthlink.net/~cweese/
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