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I got myself a copy of BTZS the other week and am making my way through it. My apologies if the answers to these question comes up in later chapters.
I took a Zone System class a year and a half ago and collected a fair amount of test data during and after. At the time, I was working with FP4+, 35 mm. My Normal development time was 12 minutes in D-76, 1+3 at 68 deg F. I rated FP4 at 100. After reading the first few chapters of BTZS, I went back to my test data yesterday morning and calculated the average gradient ("G-bar") for 14, 12, and 10 minutes development - nominally N+1, N, and N-1. I calculated G-bar = 0.38, 0.37, and 0.31, respectively. (I think I may have only developed the "14 minute" roll for 13 minutes.) I'm not looking at BTZS right now, I think the comment was 0.49 < G-bar < 0.54 was normal for most people. Why are my G-bar values so low? I was printing on Ilford Multigrade IV RC with a #2.5 filter when I went through the process of determining N, N-plus, and N-minus. I analyzed my paper curve data yesterday and I was getting ES~0.91, which I have the impression is within the bounds of normal.
On a related note, I bought a bottle of DDX several months ago and developed several test rolls of 35 mm FP4 to see how the DDX compared with D-76. I followed Ilford's recommendation for dilution, development time, and agitation (10 minutes with 1+4) and the negatives came out far more dense than with my D-76 process. Frames exposed as Zone V came out like my Zone X in D-76. I would have had a heck of time printing DDX-developed negatives with reasonable SBR if I'd followed Ilford's directions; however, G-bar for those negatives came out to be 0.54, supposedly normal. I experimented with lower dilutions to see if I could come up with D-76-like characteristic curves: 1+14 at 68 F came very close.
I'm fairly happy with how my D-76 1+3 negatives print, but am I losing something by having negatives with such low G-bar values? Was I overlooking something basic in figuring my normal development time?
Thanks,
Chris
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