Re: Speed Point in PT/PD printing?

Clay,

Thanks for the observation. In a private email Dick Arentz told me
that because of the "lousy shadow separation" of pt/pd he also uses
90% of Dmax as the speed point. I could see intuitively that neither
the silver convention nor Dmax was going to provide a satisfactory
basis for relative comparison of light sources but had never seen it
expressed anywhere exactly what convention other pt/pd printers were
using.

BTW, when you start to make carbon prints you will find that the
effective speed point is about 96-99% of Dmax, and shadow separation
is excellent.

Sandy

>Sandy:
>
>I use the 90% point as a basis for determining speed changes when I
>am printing. It just seems to make more sense to me to use the
>exposure time to get the black in the right place, and let the
>contrast control (developer, Na2, whatever) get the highlights in
>the proper place. And any of this is just to give me a starting
>point for a test strip, where I make the real judgments. I agree
>that everyone has different methods and so forth that can change
>what Dmax may mean, but using a 90% black (or whatever) would
>certainly be worthwhile in comparing the *relative* printing speeds
>from different light sources.
>
>
>clay
>
>
>On Saturday, November 8, 2003, at 01:14 PM, Sandy King wrote:
>
>>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: Sandy King
>>
>>To: 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 14:21:05 2003