Re: Great Enl. Negs - Better

Richard Knoppow (dickburk@ix.netcom.com)
Wed, 28 Jan 1998 22:13:11 -0800

At 02:05 AM 1/29/98 -0400, Sandy King wrote:
>Carl,
Lots of stuff snipped...
>
>Richard Knoppow writes: "Unless alternative printing materials have much
>different spectral characteristic then I think they do (sensitive to blue
>and near UV, with no effect on contrast caused by the color of the exposing
>light) a Pyro negative should print no differently than a somewhat higher
>contrast negative made with a non-staining developer."
>
>This statement is clearly at odds with my experience with carbon printing.
>To the contrary, as Kerik comments with respect to platinum/palladium
>printing, what I observe is that the range of highlights is greatly
>extended. Perhaps the theory of Richard's reasoning is flawed because it
>does not take into account the fact that the sensitivity of some of the
>alternative process emulsions extends into the green portion of the
>spectrum. From testing I did a couple of years ago I found that dichromated
>gelatin has considerable sensitivity to light at 500-600 na, and even
>beyond.
>
Even so that would simply reduce the effective contrast of the negative,
since, presumably, the stain is exactly proportional to the silver density.
Unless the contrast of the printing material changes with the color of the
exposing light. That may, in fact, be the case. Has anyone actually
measured this?
----
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com