Originally Posted by Photo Engineer
Mark;
You shift curves to evaluate their absolute shape minus speed changes. We have a method to do that at EK. We plot each curve on a sheet of paper and then shift them electronically or on a light table mechanically.
PE
I see what you mean -- you're shifting them horizontally (along X) to remove speed-differences, aligning them with toe-area or linear-area or wherever.

Since we're on the topic of evaluating density-curves, I was wondering why Kodak chose to put the right end of the "CI ruler" at 2.2. That ruler is marked 0.2 and 2.2, which gives a distance of 2.0 from the speed point. At a normal CI of 0.58, the distance of 2.0 corresponds to an X-axis distance of 1.73 using simple trig:

Xdist = 2.0*cos(arctan(0.58)) = 1.73

Converting 1.73 into stops: 1.73/0.3 = 5.75, which means that CI (at .58) assumes the scene contains 5.75 stops of luminance-range. Isn't that too low? I thought scenes contained a larger range than that, around 7 stops. It appears that CI is ignoring some of the highlights. Or did I miss something?

Mark Overton