From: Katharine Thayer (kthayer@pacifier.com)
Date: 04/02/02-03:51:37 AM Z
FDanB@aol.com wrote: [on March 8, 2002]
>
>
> This takes us back to the Spectral Density approach. There may be other
> ways to make the 1280/1290 produce great platinum or cyanotype negs (and
> I hope someone suggests one) but the colorization method seems like a
> good bet for now.
>
I've been puzzling about spectral density and hope there's someone here
with enough knowledge about the physics and psychology of the
electromagnetic spectrum to help me understand the things I'm puzzling
over.
Both pyro-stained negatives (the ones I've seen are light yellow-green)
and Dan's orange colorized negatives are said to block the UV
wavelengths that the platinum process responds to. My understanding of
reasoning behind this is that the orange or the yellow-green is the
complement of the UV wavelengths in question and therefore absorbs them
rather than passing them through. Which color (orange or yellow-green)
is closest to the exact complement of peak sensitivity? And my more
fundamental question is, how does one determine the color complement of
wavelengths that aren't on the color wheel? Sorry if this seems like a
stupid question, but I'm having trouble wrapping my mind around this
whole spectral density idea.
And are the sensitizers used in platinum and gum sensitive to the same
UV wavelengths or to different wavelengths; my further question being
does it make sense to use the same colors for the different processes?
Thanks for any "light" anyone can shed on this for me.
Katharine Thayer
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