Archived posting to the Leica Users Group, 1998/09/04[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
Maybe some of you darkroom wizards can help me with this one: Before heading to China earlier this summer, I purchased 200' of Tmax 400, ran film speed tests and determined that the optimum speed was 100. Unfortunately, upon my return, I found I had made a number of mistakes during my testing, mostly due to the fact that I had not read Kodak's XTOL data sheets more carefully. - -I had processed the test negatives in a 1:3 dilution of XTOL, but in my Jobo tank, this means that there was only about 125 ml of concentrated developer for 2x rolls of film--well below Kodak's recommendations. - -With these mistakes corrected, it now seems as if ISO 400 is about the optimum film speed, though my results seem to vary some from batch to batch-not sure if this is due to my exposure technique (below) or processing. (should I get a Jobo CPE-2, even though it looks like a $500 dishpan?) So, my undeveloped film would seem to be overexposed by two stops, and I'm wondering what my best course of action is. I know from Fred Picker's book, how I determine optimum film speed settings and processing times. But how does one determine optimum processing temperatures? And this is probably a dumb question regarding the M6 meter, but...I did some Zone I - Zone V test exposures using the black side of my focusing cloth as the target, and later did the same, using the white side (both times, under open shade conditions). I metered very carefully, but the results are not the same! I'd have thought that, regardless of the surface being metered, if one lights up the two LEDs, that's exactly Zone V, period. Am I encountering some sort of nonlinearity in the meter's response, and if so, should I re-do the film speed tests using a standardized target, such as an 18% grey card?