I see little benefit and a substantial cost to having a higher slope in the highlights. If one prints so that shadows and midtones have normal contrast, then the highlights block up more. What good is that?
If both batches of Kodak film look the same in D76 at the recommended times/temps, then there is an interesting question here. Can you try that test? you see, there are some classes of developer that just cannot develop some films correctly.
As for the Fuji film, either there is not enough fast component or the slow component is too fast or both.
A question about toes:
Notice the toe between densities of .1 and .2 in the graphs below:
Attachment 62156Attachment 62157
In both, D316 has a slightly softer toe than XTOL. The difference is small, but I see it often enough to know it's really there.
How can I boost the toe?
Would reducing buffering by reducing ascorbic acid (AA) and metaborate help? Reducing AA would also restore phenidone less in dense areas (or so my theory goes). Maybe adding KBr or BZT?
Mark, it is pretty tough to evaluate the data in those curves the way the data is presented. I'm not sure that there is a significant difference though.
I ran a roll of TMY2 batch 0167 through D-76. The curves (using two lenses):
There's a small inflection at X=-1.4. That also is the location of the transition between the lower and upper rows of the Stouffer step-wedge, suggesting the problem is uneven illumination. But curves for other films look fine, with no inflection there, so maybe that's just a coincidence. It's hard for me to say, and I'm going to change illumination to hopefully insure uniformity by adding more diffusion.
On a different topic, I plan to reduce both metaborate and ascorbic acid in D316 to see what effect that has on the toe. Some similar experiments I did a few months ago look encouraging.
Michael R: If you re-measure Acros, could you post the curve? Or maybe post the numbers and I can plot them using gnuplot and will post that. Thanks!
This seems to be a case of the two films being within an hair of each other in D76, but wildly different in your developer. I've seen that and have mentioned my 13 developer experiment where several coatings gave me different results in 12 of the developers but were identical in the release developer.
This means that your work is not done. If different releases of the same product look alike in a standard developer, but look very different in your developer there may be something wrong with your developer. One way to confirm this is to use another accepted developer such as HC110 to see what happens. If these two films are the same, then the fault lies within the developer and not the coating in the sense of this severe variability.
That does not mean that these coatings are good IMHO. The curves still sag too much in the middle.
Thanks for continuing your work. This continues to be a fascinating thread.
That big inflection is my fault. I'm learning that it's difficult to photograph a back-lit step-wedge through a lens. A uniform light-source usually isn't uniform enough, and lenses introduce variation in brightness from centre (spelled correctly :) ) to corner, especially wide open. Here are results after supposedly fixing the problem:
My developer (D316) and XTOL are close, and not wildly different, so I think D316 is fine. The curves are much better, but that inflection is still there in both. Rather than blame Kodak, I'm going to assume this is entirely my fault and (1) add more diffusion to the light-source and (2) use a longer lens. I like Michael R's method of simply taking a bunch of shots at various f-stops of a known light-source.
@Michael R: Flare is another problem that your method avoids. I've recently started taking two shots of the step-wedge, the 2nd with the upper row of wedges blocked to eliminate their blast of light that adds flare to the bottom row. You are correct: That flare pushes up the toe-area. The only reason I'm still trying to get step-wedges to work is so that when experimenting with developer formulas, I can develop two-frame-long strips instead of a roll at a time. I'm interested in seeing your results, and TIA for doing those measurements.