William Laven (wmlaven@platinotype.com)
Sat, 02 Jan 1999 13:39:10 -0800 (PST)
>William Laven wrote:
>
>>I finally got my POP printer friend over to compare prints exposed on her
>>Black Light 360nm bulbs vs. my Super Actinic 420nm's. Her prints were
>>exposed in half the usual time (10 mins. vs. 20 mins.) and were at least a
>>grade higher in contrast.
>
>Were these tests performed in the same fixture before and after changing
>bulbs, or are the BL results from her fixture and the SA results from yours?
>
>If the latter, they don't really tell very much without knowing in great
>detail about both fixtures (and even then, if the fixtures aren't nearly
>identical).
>
>By POP, what do you mean -- home-coated salted paper or Centennial POP?
>
>Charles
Same fixtures, different bulbs. Centennial paper.
Granted we should keep as many variables constant as possible, ie same
fixtures/ballasts, same age bulbs, etc, but in an imperfect world (Buddhism
aside) we can accept a little bit of slop. For example, if different
printers were used, but with the same wattage ballasts, I would be happy
with the results. And bulbs will always have slightly different burn times
(unless both are brand new) buit I'm willing to acept the results then,
too, with a little salt. That is, if we found the difference to be only
10%, I'd write it off to other variables, but when the difference is so
dramatic (in both exposure times and contrast) then the clear thing that's
making the difference is the spectrum of the bulbs, not the differences in
bulb age or possibly minor differences in same-wattage ballasts.
*************************************************************************
WILLIAM LAVEN PHOTOGRAPHY
Workshops and tutorials in Platinum/Palladium printing and Zone System.
1931 23rd Street, San Francisco, CA, 94107
415-647-9432 (voice) 415-647-9438 (fax)
wmlaven@platinotype.com
http://www.platinotype.com
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