William Laven (wmlaven@platinotype.com)
Tue, 29 Jun 1999 12:03:06 -0700 (PDT)
>
>There are clearly reciprocity/contrast effects occurring, accented by the
>self-masking. It is most probably not the wavelength difference causing the
>contrast difference, but this is my feeling from observation and
>experience and
>was not tested.
>
>Conclusion- Yes, they're faster, but probably not for the reasons that have
>been discussed here. A Shelby Cobra is faster than a Corvette (similar
>vintage), but not because one's red and one blue, but because the Cobra is a
>Corvette on steroids. It's hard to beat more horsepower in less space. (I
>know
>there are a lot more differences- please car guys- don't jump on me- making an
>analogy)
>
>The solution to the original problem? Remake all the negative so they print
>under six minutes in my darkroom.
>
When I ran my tests of BL's vs. SA's, they were same length, same wattage
bulbs, all new and printed in the same exposure unit (ie the same ballasts
were used) so there were no variables as you've described in the above
situation (spectrum, power, reflectors). I think, then, that the spectrum
does account for the difference.
Your solution, though, is a wise one: make negatives for one's own system
so the print times are reasonable and the prints are good. As we all know,
Pt/Pd responds to zillions of variables which makes what is a challenge for
some a pain in the ass for others. Therefore, maybe other variables exist
which account for the different printing times which neither I nor others
could imagine.
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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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