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Phil pointed out to me that BTZS tests on stained negatives are questionable. I decided to check out why. I used the blue channel for data and max density for 0.04 over paper base is 1.48 (determined using a stained step tablet, and IDmax% = 100). For AZO and using pyrocatHD (2-2-100): At 70 degrees my normal negative is 8 minutes (from practical tests). When I ran the series of BTZS tests (5 films 4, 5.5 , 8, 11, & 16 minutes) and doing the graph by hand, at 8 minutes one would expect the zone ruler to "lineup" and indicate N. It does not. So I made a zone ruler (my "normal ruler") to fit my 8 min data and used it for all other BTZS calculations.
The only data from the test that will fit in plotter is my 4 minutes test. The series is overexposed by 1/3 stop (OK for hand drawing, but plotter needs a fb+f value in the series). For ES 1.28 (1.48 - fb+f) plotter indicates appx. N-2.1, where my hand data indicates N-1.5. A closer look indicates without adjustment that plotter yields results closer to the ZS.
A couple of negatives indicate my hand-drawn data and "normal ruler" results are trustworthy. However I recognize that even these results contain error as the stain is different at different exposure. But it gets me closer. To verify my tests I checkout the III-VII spread on non-test negatives.
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