RE: Speed Point in PT/PD printing?

Sandy, Have you looked at Mike Wares info on PT/PD printing in relation to
moles of PT and/or PD produced at various wave lengths? You might be able to
establish a speed point for a PT/PD mixture but with the variations
possible, WHY/

Eric Neilsen Photography
4101 Commerce Street
Suite 9
Dallas, TX 75226
http://e.neilsen.home.att.net
http://ericneilsenphotography.com
 

> -----Original Message-----
> From: Sandy King [mailto:sanking@clemson.edu]
> Sent: Saturday, November 08, 2003 2:19 PM
> To: alt-photo-process-l@sask.usask.ca
> Subject: 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 Sun Nov 9 13:37:51 2003