Developing Sheet Film at N - 20% : LUSENET : Large format photography : One Thread


I am still trying to figure out bits and pieces of the Zone system and ran into an interesting situation. I exposed a piece of Tri-X at f64 for 35 seconds. Then adding in extra time for reciprocity failure, came up with a final exposure of f64 for 130 seconds. According to a class I took, when compensating this much for reciprocity failure, I should decrease my development time by 20% (hence N - 20%). When my N development time is 5.5 minutes, then N-20% is 4.4 minutes. Everything I've read and heard says that you shoud never develop for less than 5 minutes.

In a case like this, where the calculated development time is under 5 minutes, how should one compensate to bring up the development time to >= 5 minutes? Should one lower the temperature of the developing solution a couple of degrees?

Thanks for all ideas/suggestions, Robert

-- Robert Ruderman (, April 30, 1999


First, the minimum developing time (for complete even development without streaks, uneven areas, etc.) depends on the method. I tray develop and routinely develop Tri-X and T-Max for 4.5 minutes with excellent results. Other avenues to explore to reach an "N-20%": dilute developer solutions, lower temperature and, of course, a different developer entirely. With the these last you must first find the time for N and then subtract your 20%. Experiment, experiment and you'll have no trouble finding the answer. Hope this helps. ;^D>

-- Doremus Scudder (, April 30, 1999.

I'd be inclined to dilute the developer more rather than go to shorter times.

-- John Hicks / John's Camera Shop (, April 30, 1999.

I've got very good experiences with varying dilutions with HC110 to control contrast. I agree that development should not be too short or too long. I prefer - intuitively - between 6 - 8 minutes, otherwise I'll choose another dilution. Changing temperature is not my choice, it's more error-prone. Recently I use Rodinal, but varying dilutions here does not seem that predictable as with HC110 (so far, which is not very far yet).

-- Lot (, May 02, 1999.

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