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 11:40:40 2003