I was thinking of a (perhaps) clearer way to explain what I meant in my post above, which is probably too wordy. I think the fractional gradient constant 0.3 produces the first excellent print under all/most development circumstances when the original scene has a normal luminance range. If on the other hand, one deliberately reduces development to manage a scene of higher than normal subject contrast, the first excellent print might only come from a fractional gradient relationship of 0.4G or 0.6G etc. In other words, the fraction, rather than being a constant, could be related somehow to the subject luminance range. Or said even another way, the fraction could be inversely related to G. This would be a possible bridge between print judgement speeds (or fractional gradient speeds) and the variable EIs people arrive at in their ZS testing using a fixed density criterion with +/- development. The speed methods deal with a standard, while applied densitometry systems like ZS deal with the management of scene luminance ranges.
Note this concerns film speeds for different Gs, not the difference between a normal ZS EI and ISO speed.
Again these are just some preliminary thoughts after reviewing the papers.
Mr. Bill, didn't mean to imply the tone reproduction discussion isn't relevant. Sorry about that.
Last edited by Michael R 1974; 03-09-2013 at 07:38 PM. Click to view previous post history.