In parusing this thread, I found this to be a striking observation...............this is precisely the sentiment made clear in The Negative.....points along a curve connected by a straight line are not touted in the The Negative as having any significance toward any ZS analysis of characteristic curves. It's the comparison of two curves in their entirety that provides the best evaluation of a film in a developer, so says the author. Gamma, which applies to "true" straightnline portions of any curve, is given more merit than points connected by a straightline. Whether this is agreed with or not is kind of beside the point, it's just an observation. I don't bother with CI myself, I just compare the curves, I find that to be most illuminating and the most straight forward.
Originally Posted by Michael R 1974