Compensation by Intermittent Immersion -- followup

I finally managed to scan the test negatives developed by intermittent

immersion (see my previous threads, <a

href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=007Go9">here</a>

and <a

href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=007PWA">here</a>).

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.<p>

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.<p>

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.<p>

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.<p>

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.