William Laven (wmlaven@platinotype.com)
Sun, 03 Jan 1999 11:02:07 -0800 (PST)
Supposedly the major sensitivity of a "platinum"
>print is at 412 nanometers, while gum bichromate is at 360 nm.
Where did you get that info? Do you know the sensitivity peaks of other
materials. This is just the kind of info more of us need. There might be
experimental data out there which would add to the anecdotal evidince.
>
>However, a different emulsion, even nominally of a "platinum" print may
>well have a different sensitivity. For example, we know from tests a
>couple of years ago, that carbon sensitivity is different from gum, even
>though both use ammonium dichromate. Sandy (as I recall) did tests with
>carbon where a daylight fluorescent improved contrast, but in my tests
>with gum the same bulbs were 3 times slower & much too contrasty.
It would be nice if someone compiled all this anecdotal and experimental
data. I only work with Pt/Pd so only know how it responds.
>
>As I say, for what that's worth.
>
>Do they tell you the spectrum of the superactinics?
I have a graph of my bulbs output (supplied by Philips, the manufacturer)
and it peaks at 420nm and has a very narrow spectrum output so its great
for Pt/Pd (and POP it seems) since it concentrates its energy just where we
need it.
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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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