In the original post to this thread Walker wrote:
It might be a good idea for the benefit of everyone using the Pro inks for making digital negatives to take advantage of this. 
Keith
This is a good idea, but first I would like to understand how the restriction affects linearization.
Is there a dependence on the steepness of the curve?
Could linearization be more successful with a less dense master curve?
vs
To avoid confusion, the proper term here is limit, not restriction. They are not synonymous in this context.
The purpose of limiting is to match the density range (DR) of the negative to the exposure scale (ES) of the printing process. (Please note that changes in the printing process — even those that may seem to be small — can have a significant effect on ES. Examples include change in amount of restrainer, change of developer, change of paper, &c.) The correct limit must be determined and incorporated into a customized Master quad before linearization can be done.
Given the same negative such as a 21-step Stouffer step-tablet:
More visible steps = Longer ES process = lower contrast in the print —> needs higher DR in negative
Fewer visible steps = Shorter ES process = higher contrast in the print —> needs lower DR in negative
In your example Ps curves above, the 2nd produces lower contrast than the first and is suitable as a starting point for a process with higher contrast (lower ES). I do think though that it’s probably too low for your current situation. I think something like this will get you in the ballpark if you want to stick with 1 drop of 5% Na2:
I still recommend reducing the Na2 down to 1 drop of 2.5% or 1.25%, in which case a limit like your first example above will probably be closer. Either way, you need to make a decision on this before before proceeding with the limiting step.
From your use of Ps curves here, I’m guessing that you have the basic PiezoDN (v1) tools rather than the Piezography Professional (PP) tools, and that you are following the directions in the Piezography Manual for limiting a quad. This is a situation where the PP tools would be useful since there are things you can do with it that you really can’t do with v1.
I am not using the Pro inks myself so I can’t test anything with them here, but I can make an modified master for you based on an educated guess if you want to try that.
Keith
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The density scale between this pro curve and traditional Selenium PiezoDN curves is not much different. In this case I’m pretty sure that your blown out highlights are a case of NA2. That being said, I’m planning on publishing a series of contrast rations (once I get the names proper!) shortly.
-Walker
Thanks Keith!
I forgot to fix it in the translator.
What I see:
even in the absence of a contrast agent, in order to rise to 150, I need to increase the exposure time to 10 minutes. In general, this is not a problem. I printed from silver negatives for 15 minutes without fog.
Walker writes that the exposure was 175 units, I understand that this value is arbitrary, but for example, on my amergraph with a mercury lamp, the exposure with OEM ink was about 70 units (I have not tested pro ink yet)
I selected the exposure for the blb and mercury lamp based on the maximum blackening for the pictorico film
Your suggestion is interesting, because I can’t understand how the limit affects print curves. I suspect there may be problems in steep places.
also refusing Na2 I reduce Dmax to 1.35 instead of 1.6
Must be a typo here, isn’t it 56% RH ?
Curve was calibrated originally for 46%. Why? Because higher humidities would create a more sensitive coating that would require more density and it would be harder for other mediums and humidities to calibrate/limit to the master. Already too dense as is thus my last post.
Don’t take my lack of explanation of source data differing from published salt bath RHs as dropping the ball. I simply do not have the time to fully explain sometimes.
-W
x8xx Cyanotype and PtPd Develop Out starting curves.
Pro-PiezoDN-Cyanotype.quad (8.1 KB) Pro-PiezoDN-PtPd-DevOut.quad (8.0 KB)
I believe the cyano will work for Vandyke Brown too . . . these are just best guesses.
best,
Walker
Hi Walker! for pt/pd, are these curves with a reduced density?
yes they are with reduced density