I'd suggest doing more repeats and averaging the results. I'm not an engineer, but my two cents as a printer: on the first graph I'd call the difference in highlight gradation slight at most. Contrast with XTOL is a little lower between x=2.3 and x~2.7, but after that contrast is essentially identical to D316. So I'd be surprised if the divergence at x=2.3 has anything to do with buffering. One would expect less buffering to reduce highlight densities/contrast, but the difference between the curves should keep increasing (at least that's what I'd expect). To me it looks like the occasionally kinked curves I've gotten with XTOL. On the second graph while I'm not surprised the curves are the same for a ~4% change in development time (within normal margin of error in my opinion), I am somewhat surprised you found such a marked increase in grain with such a small difference in development time, and without an apparent increase in density.

Regards
Michael

Quote Originally Posted by albada View Post
Here's the comparison of XTOL and D316 for Tri-X. These are 36-shot rolls, not test-strips:

Attachment 60096

The density-curves match almost exactly up to X=2.3. But an interesting thing happens after X=2.3: XTOL's slope suddenly drops, but D316's slope stays unchanged, causing the curves to diverge. If you ask me, XTOL's curve will cause worse gradation in highlights than D316, because D316 remains more linear through the highlights. If I were a user of Tri-X/XTOL, I'd be annoyed at the worse gradation in clouds, snow and white clothing. D316's curve is better.

That sudden slope-drop in XTOL is odd. Any idea of the cause of that drop or the lack of drop in D316? Did I overdevelop D316? Or is the better buffering in D316 causing highlights to stay on track better?

Mark Overton

EDIT:

It gets stranger. Here are plots of D316 at 13 and 13.5 minutes:

Attachment 60098

They look almost the same! But grain is definitely better at 13 minutes, matching XTOL in my loupes. It seems that increasing time boosted grain but not density. Maybe I'll try 12.5 minutes for the fun of it.