This may be very well too technical. I think PE and Stephen both are right and possible wrong. I find this difficult to understand. Won't you all come to Berlin and give me a lecture please.
Graphs are rather abstract, for some more than others. Now I don't have the desire to go reading long fat books about this stuff. It takes a lot of time and money.
When I try to explain just the film curve to some people I know they have a problem understanding that. That is the first simple basic step.
What I do miss from the beginning, at least that is my felling is that the comunication between film makers and photographers is missing.
The why and the how.
Yes the BTZS program does help in this.
This all certainly opens up to concidering more what is involved. Certainly way more than saying use this film/paper it is good. When few can say why.