Can someone tell me (it was referred to in another post, but I can't find the relevant thread) about the "quick diagnosis" of thin negatives - how to you distinquish underexposed v. underdeveloped, are there any giveaways in the negative that will lean it towards one or the other? I have been using APX100 (4x5) rated at 64, with Rodinal 1:50 and am having a devil of a time pinning down "normal" development time, looking for help on "cues" in the negative that will indicate if my incosistency is in development or exposure. thanks!

-- andy (drewu3000@aol.com), September 07, 2001

Answers

Generally, if the negatives lack shadow detail, exposure is inadequate. If they have shadow detail but lack contrast, development is the problem.

-- Jim Steele (jdsteele@hotmail.com), September 07, 2001.

I would use the "hard way" to solve your problem: First determine your actual film speed with your developer. A very workable way to do this is in the Kodak book on advanced B&W photography (but there are also many other sources). In short: You use controlled underexposure to determine film speed. Rodinal generally gives very consistend results. I use Calbe R09, the "classic" Rodinal formula and I never had problems getting repeatable results. Also APX is a very reliable film which works fine with Rodinal. It might be that your speed is still too high. After finding out the "true" film speed for your system (which will also calibrate it according to your shutter, exposure meter etc.) you can determine the developing time by calibrating zone VII according to the paper contrast you want to use. Information again in the afore mentioned Kodak book. It may take some time and a little material, but it is worth the effort. Only with these tests you can be reasonably sure that the system is calibrated.

-- Volker Schier (Volker.Schier@fen-net.de), September 07, 2001.

Andy, the quick answer (that I can recall) to distinguishing between an underdeveloped versus an underexposed negative is to look at the edge markings. If they are gray instead of black then the negative is underdeveloped.

If you've already established EI 64 with APX 100 by calibrating your shutter, meter, and developer then please ignore the rest of this response. If you haven't then you'll have to find your EI first before looking for your normal development time. The conventional measure for the right EI given your equipment and procedures is 0.1 density units above the film base + fog.

Here's a link to an old (two part) article by Tom Halfhill on personalizing your film speed. If you prefer the calibration method mentioned in Adams' "The Negative" then you might find this Zone System site interesting. The best hint I read for testing film is to use a diffuser.

-- Bong Munoz (bong@techie.com), September 07, 2001.