D23 vs Ilford Perceptol?

jim appleyard said:

Patrick, I'm sure you've heard of "compensating devs"; keeping the highlights from blocking up too much and also letting in some light to the shadows. Well, a "semi-compensating dev" allows this to happen to a lesser degree.

No, there is no scientific definition, AFAIK, and I don't think I could tell which was which. I think amount of "semi" depends on how much you dilute the dev. It might be one of those definitions that falls into the same catagory as "a little bit pregnant"

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Of course, I have heard of them, but usually it is because someone is trying to predict the behavior of a developer by looking at the composition who in fact has not used the developer. No one has, to my knowledge, even defined compensating satisfactorilly. I saw a diagram on the information that came with Acutol (IIRC) that showed a characteristic curve that was convex upward like an inverse exponential function that you see on gamma vs time of development curves. This was NOT an experimental curve but someone's theory. I wouldn't want such a curve even if it were real. It would not match any available paper curve.

"Semi" literally means "half" does it not? I'm reminded of the jokes we used to make about the Semi latus rectum in high school. Maybe we should call them "Semi rectum developers".

gainer said:

No one has, to my knowledge, even defined
compensating satisfactorilly.

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Compensate: to counterbalance, offset. Why the need to
compensate? The need arises with slow speed films and their
inherent high contrast. Compensating developers are highly
active and highly diluted. The mechanism of their working
is developer depletion in areas of most density.

Carbonated film developers such as FX-1, Beutlers, and
quite a few others including the lye powered Rodinal are
examples. Some paper developers fit well the conditions
for a film compensating developer. Dan

dancqu said:

Compensate: to counterbalance, offset. Why the need to
compensate? The need arises with slow speed films and their
inherent high contrast. Compensating developers are highly
active and highly diluted. The mechanism of their working
is developer depletion in areas of most density.

Carbonated film developers such as FX-1, Beutlers, and
quite a few others including the lye powered Rodinal are
examples. Some paper developers fit well the conditions
for a film compensating developer. Dan

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Many years ago (probably 20+ when I was a college student with lots of extra time) I tested about 8 different developers with 4x5 Tri-X. My two favorites were D-23 and Rodinal. I guess I like the effect of the compensating developers.