I’m happy (and somewhat surprised) to be able to report success at creating a digital “Pseudo Stouffer” 21-step negative. There were some glitches in the software, and I had to do a few unorthodox (or at least undocumented) procedures to get past them, but in the end I am able to make a 21-step negative that is closer to ideal than the tolerances in Stouffer’s own specifications.
Here is a graph from PPEv2.1.0 of my final result:
And the Measurements and Target-Measurements:
One of the first things I learned was that the target measurements have to be adjusted for the film base density - in this case 0.14 - rather than use the Stouffer film base density of 0.05.
The second strange thing was that the Measurements data had to be shifted down one row to avoid the top value being cut off on the Home sheet. Typing the corrections into the New L* column did not work; shifting them down in the Measurements sheet did work so I went with it.
A third thing, one that I might have anticipated and done first, was that leaving a high Dmax as we do for the black mask (and step 1) of a regular negative caused problems. I believe this is due to the small number of input values. I wasted a few iterations trying to avoid it, but after reducing the start point down to where it gave me the correct step 1 value (3.14) the rest mostly fell into place.
Probably also related to the small number of input values, the shadow end (thin end of the negative) was not being corrected by normal means. It was obvious what needed to be done - pull that section down a bit - so I used the New Curve…Tweaking to do it manually.
This still left some awkward humps in the individual channels involved. Putting the New Curve into the Starting Curve position (in a fresh instance of the spreadsheet) and applying channel curve smoothing affected all the channels which I did not want. So I wondered what would happen if I just pasted in one channel at a time. This worked beautifully for the 2 channels in question, and I simply pasted the smoothed channel data back into it’s proper place in the quad. The result is seen in the first screenshot above.
I did all of this with the beta PiezoDN Dye inks that a few of us are currently testing, so the actual quad is probably not useful to anyone but me (though I’ll be happy to share it), but I think we can consider this to be validation of the concept.