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Per your recommendation, I visited and read the material on http://btzs.org/Articles.htm (ref. b.).
I have attached some questions and comments.
My results suggest that my testing was reasonably well done. Considering that photographic process has opportunities for only a certain amount of practical control, I , nonetheless, would be interested in more precise usable results.
Based upon a better understanding of what your test(s) will produce, I would be interested in having you perform tests for me (I hate testing so, other than my initial Zone testing (Personal film speed, Normal development time, and those for N-1, N-2, N+1, & N+2), I make adjustment empirically. For exposure adjustment for different N values, I currently use Bruce Barnbaum’s estimates for Tri-X.
Perhaps this is a timely discussion since Kodak’s new Tri-X manufacturing plant has required Kodak to recommend certain reductions in development time (they only give a range to work within to pin point development time).
My process is as follows:
Tray development using HC110
Only six sheet of 4 x 5 are developed at one time.
Shuffle is one sheet every 10 seconds. After 6-sheet, 90º rotation.
Paper
Primary: Polymax Fine Art VC
When a more neutral tone is desired, Iadd some Benzotriozole.
Occasional: Agfa Multicontrast Classic VC when warm tone is desired.
Englarger
Beseler 45 MX
Head: Zone VI Variable Contrast Cold Light
Temperature compensated timer
Zone VI Compensating Timer for film & paper (a thermister based electronic circuit approximating the curve for most b & w film (not Tmax) and all papers.
Laboratory is safelight tested and all white light leaks are suppressed.
Any comments you can make by return e-mail would be appreciated. Regardless, I will give you a call next week.
Meanwhile, thank you for your time late in the day last Tuesday afternoon.
Attachment:
Reading the Test Data
• Emin/Emax – min/max range that defines the limit of the test images exposure range
• SBR – This corresponds with the “subject luminance range (SBR) of the real pictorial image.
What do you mean by “real pictorial image”?
• G-bar - Slope of the curve is averaged to provide “average gradient” (G-bar). This is precise indication of development extent.
You are talking about the a value for density, right?
Why do you want to “average” G-bar gradient?
• EFS value – Working film speed based on average G-bar equivalent to 0.62 of standard ISO rating by film manufacturers
This is the figure Kodak uses? They call it “Contrast Index?
• Practical working speed of the film/developer combination on any subject range and development condition.
Effective or actual speed of the film?
1. What assumptions does your software program make regarding how to introduce flair into your estimates?
2. How do you relate this to the paper that I use?
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