Re: Speed Point in PT/PD printing?

I have plotted quite a number of curves ranging from prints made with
pure platinum to various mixtures of pt/pd to pure palladium so I am
well aware of the fact that the shape of the curve varies a lot
depending on the exact composition of the sensitizer, and other
factors as well.

The issue is that one type of light might indicate a higher effective
printing speed than another if you set the speed point as in the
silver convention, but if you set the point at 90% of Dmax the
opposite could very well be true. In my own work I always establish
exposure time by about 95% of Dmax, and then adjust other conditions
for contrast. How do other workers determine the best exposure time
when evaluating a pt/pd test print?

Sandy

>Sandy,
>
>For starters, the issue of maximum black for PT/PD prints is in
>itself a question. This seems to be primarily because of the
>methodologies in use from one printer to the next. Unlike a given
>piece of manufactured paper with it's absolute formula for a
>sensitized coating, a PT/PD print can take on any number of
>appearances based solely on the operators tendencies, methods and/or
>for artistic purpose, an intentional or unintentional breaking of
>the normal rules for printing PT/PD. The combinations as you know,
>are endless.
>
>n
>
>
>----- Original Message -----
>From: <mailto:sanking@clemson.edu>Sandy King
>To:
><mailto:alt-photo-process-l@skyway.usask.ca>alt-photo-process-l@skyway.usask.ca
>Sent: Saturday, November 08, 2003 9:38 AM
>Subject: Speed Point in PT/PD printing?
>
>I am preparing an appendix on UV light sources for a book on Pt/Pd
>printing and I have some questions about speed point convention that
>need to be addressed in my comparison of different light sources.
>
>In silver printing the speed point is defined by ANSI standards as
>the exposure necessary to produce a print density of log 0.6 over
>B+F.
>
>In carbon printing, where we have an almost perfectly straight and
>linear curve, it has been my experience that the silver convention
>is not the most logical way to establish the effective printing
>speed of different light sources and I usually find that the point
>on the curve that has the first maximum black, or some very high
>percentage of maximum black, is a better indicator.
>
>But the pt/pd curve is of course quite different from both a silver
>and carbon curve, in fact somewhat intermediary between the two. So
>I am wondering how we should determine the speed point for for
>pt/pd printing? Do you think the silver printing convention is a
>good indicator, or would it be better to set the the point at Dmax,
>or at some percentage of Dmax? Or at some other point?
>
>Any thoughts on this by pt/pd printers would be appreciated.
>
>Sandy King
Received on Sat Nov 8 13:15:59 2003