Quote Originally Posted by markbarendt View Post
It seems to me that if we use any given negative film, processed in a given and consistent developing regime; that a given amount of exposure, should get us a given film density at the same point on the curve every time.

I see no reason or evidence in my own experience to suggest that I should expect inconsistent results, except for flare. So it seems to me that because of flare the actual/effective speed point for any given shot in the field would actually be the least knowable point on the curve.
Mark, I was speaking generally. It's a question of what is knowable. Zone System testing defines two points (both mistakenly). Even if they were accurately defined, there isn't any information with what goes on in between. Exposure isn't about that anyway. For black and white negative films, it's about placing the subject luminance range on a part of the film curve that will produce a quality print. There really isn't a correct exposure. That's why Zone System's EIs are usually half of the ISO and the old ASA speeds were half of the current and there's no problem in quality. The primary reasons to keep the exposure as short as possible is to keep printing times a short, limiting grain and light piping, and maximizing sharpness.

Doremus, nicely said. I do have a conceptual problem with just black printing / proper proofs, but that's a topic for another thread. People mistakenly think I'm about extreme control. I'm not. I'm about correct understanding.