Compensation by Intermittent Immersion -- followup

Discussion in 'Black and White' started by silent1, Feb 21, 2004.

  1. I finally managed to scan the test negatives developed by intermittent immersion (see my previous threads, here and here). As reported previously, these TMY 120 negatives, developed 50% longer than my "normal" for TMY in the top half of a half-full double 120 tank, were distinctly overdeveloped. In fact, the first four frames, shot at normal exposure, were so dense I couldn't get a usable scan from them on my Agfa Arcus 1200 -- a newer scanner might have done better, since some newer scanners can handle about 25% higher density than this one, but this is the only one I have access to.
    The remaining four frames, however, shot at -1 stop exposure, while still dense, were scannable, and appear to show similar shadow detail to normal exposure, normal development negatives shot at the same location and within a few minutes. It's difficult to be certain, because of my poor choice of test subject -- all the genuine shadows are leaves near the camera, and as such it's somewhat difficult to examine them for captured detail -- but it appears there may have been a small increase in real film speed, perhaps 1/2 to 1 stop. Unfortunately, the overdevelopment raises the question of whether this is just what would be seen with conventional push processing, which is also reported to capture an additional 1/2 to 1 stop of shadow detail with a two stop push.
    It is certain that grain was increased, as would be expected with overdeveloped negatives, but overall tonality was better than I would normally expect for the two-stop push that would give the apparent increase in shadow detail; in addition, in spite of the overdevelopment, I can clearly see some compensation effect in the form of preserved highlight detail compared to the same area of sunlit clouds on the control roll.
    What all this talk boils down to is that, pending additional testing aimed, first, at establishing a "normal" development for intermittent immersion (which it now appears will be no more than 20% over standard time for normal processing, and might be no longer than standard), it's impossible to be certain, but I can see enough compensation and accompanying possible shadow speed increase to make it worth expending more film and time to test. I can also report that, at least in a closed tank where air circulation is limited, and with a low-fog developer, aerial fog isn't a significant problem with intermittent immersion.
    More to come, as I have time to shoot and develop more tests, with better chosen test subjects and more normal level of development in the test rolls.
  2. Interesting. Thanks Donald
  3. Thanks for the info, Donald.

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