New Test, New Data for Kodak 320TXP and Ilford HP5+
I have just completed a second test of 320TXP and a first one for HP5+, a film I am quite familiar with, yet which I have never tested formally. I am attaching WBM spreadsheets for both of them. As I have been reading about sensitometry, both here, thanks to your detailed posts, and in books, I am getting a better feel for the tone reproduction process, and the data that supports it. I am, at last, starting to gain a clear understanding of my materials, which is a wonderful feeling.
I will plot the curves myself, and I will try to arrive the the gradients/CIs by hand, as I am not sure if the 0.17–1.37 DR method is the one I can easily relate with my book reading. I am also calibrating my enlarger light source-paper-developer combination, and soon I will be able to use an target DR based on that analysis (plus 10-15% for average flare, I suppose).
In the meantime, have a look, if you are still following this thread, at the numbers below. These tests were performed using a contact technique, with a flash above an opal plexi diffuser (shown on this thread). I've exposed 3 sheets for each film and developing time, and I am amazed that the consistency of the flash exposure was so good. Sheets do not vary by more than 0.02 at any point (sheet-to-sheet), and, in fact, they usually read the same density for most steps (sheet-to-sheet), except for the steps 1-2, where they may vary by 0.04 at most. A test sheet exposed with an ND filter varies only 0.04 across extreme corners, so the illumination was OK for the purpose of this test.
It has not all gone very well, though. I have clearly underexposed 320TXP by a 1.3 stops, pity... Also, I have mistimed the 5.5 min development batch, as I had an incident with my timer. I think that batch is closer to 6 min, and I have tried to correct for that on the "Summary" page of the spreadsheets.
Overall, it would seem, using the WBM spreadsheet method only, that the dev times for HP5+, within 30 sec of what I am used to, are a very reasonable: N-1 at 8.5 min, N at 12 min, and N+1 at 16 min, using XTol 1+1 20˚C. I am very pleased to see those results, even though I have reduced agitation from 4 to 3 full inversions every 30 sec (plus 30 sec at the beginning). I suppose that accounts for the difference.
As for 320TXP, I do not have experience of that film, so I am not sure how to trust the dev times, bearing in mind the lack of full data due to underexposure. The spreadsheet seems to suggest: N-1 at 5 min, N at 7 min, and N+1 at 11 min. All of those use the target gradients suggested by WBM, which I remember Stephen agrees with, too, concerning the aspect of flare.
I am curious what aim DRs will I get when I measure my paper ES.
Many thanks to all for guiding me.