RE: Speed Point in PT/PD printing?

Hi Eric,

Where did you find that information? There is some comparative
information on pt/pd speed in the article on platinum printing at
Mike Ware's website but I did not see anything about wavelengths.

The information I found at the site does not help me much because, 1)
he did not test different light sources, and 2) he bases speed on mid
values, which equates more to the silver convention than to 90% of
Dmax which I consider the most logical point to measure speed.

My objective is not to establish a speed point for all of the
possible variations but merely to show with sensitometry that there
are significant differences in speed point that result not only from
the specific Pt/Pd mixture (with a given light source), but also from
the combination of Pt/Pd mixtures with light sources that peak at
different wavelengths.

Sandy

>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 14:52:16 2003