Quote Originally Posted by Michael R 1974 View Post
Mark, how are you determining speed/EI photographing the backlit wedge?
You'll laugh at this: I guess based on where various films hit .1 over B+F!
That's their ISO speed-point, and I know where that should be on the log E axis. Of course, developers shift that point, and there's no guarantee that the films themselves hit it exactly. But this gets me close. All my work has been comparative, usually comparing with XTOL's curves, so I haven't needed accurate log E numbers.

Mark