Quote Originally Posted by markbarendt View Post
The curves for TXP aren't showing it reaching D-max so, no to that part at least.

TMY can hold about 14 stops on the straight line IIRC, so if you had used TMY instead of HP5 for the shots that started this thread you could have exposed another three stops (7 stops up total) before you even got to the shoulder let alone finding D-max. So again no, the generalization doesn't work.

Hi Mark. I think you are missing my point. Here is how I would conduct the experiment so that a generalisation can be made about the curve shoulders for at least a few popular films and developer combinations:

1. Pick one of the 5 most popular B&W panchromatic films.
2. Pick one of the 5 most popular film developers.
3. Expose the film to a step tablet with sufficient intensity that causes Dmax to be reached and entered into by at least 1 stop (this guarantees you WILL eventually traverse the shoulder even if you can't find it in the published curves) when it is developed.
4. Develop the roll for some minimum time which ensures a CI beginning at say 0.3 and that Dmax is reached because it was overexposed so much in step 3.
5. Repeat the above steps, increasing the dev time to give increases in CI of reasonable steps (say 0.1 or 0.2) until you reach a CI of say 1.0.
6. Plot all HD curves for that combo on one page.
7. Repeat all above steps for a few more film+dev combos.
8. Make a general statement about what you observe in the shoulder areas of all the curve sets.


regards
Peter