I tested them both, simply can't remember what in, though. It's probably in the files somewhere. Whatever it was would have been fairly generic, most likely hc110b. I do remember the results, though, at least what I determined as a practical ISO for general use. Speedwise, it was 800 for both. Now I'm curious so I may try to find the data.

Some fewer years back I retested Δ3200 in Beutler's and for that I do have some accessible records. I worked that one up because my wife shoots Zone Plate images on it. We were looking for a combination that would give us excruciatingly sharp grain with which to present the very soft images. Turned out to be just great. Of course, though, the zp itself imposes a different and more gentle kind of gradation which is pretty forgiving at both ends; almost more like an equal increment scale, rather than typically photographic.

So here's something found in my notes for whatever it's worth:

"First impression of the wet results is typical in my experience with these high speed films in that the first visible separation in the zone tests appears to place zone one in the realm of 400 ISO.... The subject exposures ... following the zone patches was made at 1600 ISO using the camera's metering system... They are underexposed. The granularity is visible to the naked eye, and there is a beautiful uniformity to the images, which nonetheless appear to be both underexposed and underdeveloped. I suspect that the useful rating will be ISO 800, and the developing time will be around 17 minutes."

I had been living then in a barn with no densitometer and hardly a darkroom at all at the time, so I was doing these tests the old way; visual determination of separation from a controlled dead black on a contact print for the speed; marking with a sharpie on the upper zone patches enabled determination of separation from pure white on the same sheet. I know that these sheets are around somewhere. We always have to wonder, though, what they may have done to the film in the meantime. That was 8 years back.

Even back in the mid '60's visual determination was pretty marginal on zone 1; Minor White suggested working from a clearly visible zone 2 as a practical adaptation. Ansel Adams' method from the old Basic Photo series was based on films that had a lot more silver in them (apparently). I'm curious about how these tests would work with the Adox films, whether a visual zone 1 might still be there. I have a good densitometer now and a better lab setup.

Anyway, I have fair confidence in these numbers still, although with the zp's we kick the development time into the stratosphere since the negatives we get otherwise are a bit hard to deal with since they don't have enough contrast.

Phil Davis' issues with the zone system seem to be born out with your data on xtol (df); he points out that the assumption that the lower zones don't move is invalid. With more typical film/developer combos, this is true, but practical results can be achieved nonetheless. Your xtol data shows that we may need to take a closer look at the whole curve if we are interested in any kind of precision.

All this is fascinating and seductive. But maybe too complicated. I'm going back to scratching on stretched animal skins with burnt sticks.