Re: Speed Point in PT/PD printing?

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 13:38:31 2003