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Phil,
Your response raises an interesting question: in the BTZS system, how DO we check the validity of our data? In BTZS 4th ed., pp. 103-104 you write of the importance of "careful field tests." Those tests seem to entail taking photographs, noting the zone placements and using the information generated in testing; developing on the basis of our test data; making a print on our chosen paper at the chosen filtration settings; and then . . . visually assessing the results, and adjusting our working data based on that visual assessment. But if MPE is not a useful test of negative quality, then surely assessing all our objective testing on the basis of a test print MADE WITHOUT ANY OBJECTIVE CONTROLS WHATSOEVER would be even worse!
In your response to my original post you write, "although it's nice to have negatives that print at a more or less consistent exposure I think it's more important to print for best image quality rather than worrying about the actual exposure time." I agree, of course, but this entirely misses the point I was trying to make. I wasn't suggesting that having all negatives print at the same exposure was the goal; rather, I was suggesting that an incidental, but possibly useful, property of correctly produced negatives using the BTZS system and fractional-gradient-based speeds is that they would, in fact, all print at the same exposure. [Possibly with a small correction to account for changes in B+F arising from changes in development time.]
One of many things I like about BTZS is its clear separation of technical and aesthetic questions. Of course a negative that produces a great print is anything but a "total failure"; but it might still be, from the point of view of what I was hoping and expecting to produce in terms of G bar and density range, a lousy negative.
The thought (evidently not a good one) behind my original question was this: Could we not use a reflection densitometer to greatly improve upon the the old MPE test of the traditional zone system? The densitometer would allow us to determine MPE with great exactitude. We could then measure highlight and shadow densities in the print with the densitometer and relate them to the original metered values in the scene. Could we not use the densitometer to validate, in an objective manner, not only our developing times but our original zone placements and our measurement of the SBR as well? |
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