on 1/17/01 1:33 AM, pentax-discuss-digest at [EMAIL PROTECTED] wrote: > Shel Belinkoff wrote: >> >> However, apart from a 1:100 dilution, I utilized a couple of >> other techniques. First, I used minimal agitation, inverting >> and twisting the tank for only ten seconds every three >> minutes. > > I know right where you saw this...I've been planning to try it for a > while. Having been Editor of the world's leading darkroom magazine (that's like saying the world's largest buggywhip manufacturer, but whatever) for six years, I would encourage you earnest experimenters to a.) run controls, and b.) take advantage of film testing services. A leitmotif of my job for those years was that I'd regularly receive article submissions from people who were excited about reinventing the wheel and were eager to tell the world that it worked if it was round. A lot of these old techniques don't really make much difference with modern films--water bath, split developers, intermittent agitation, extreme dilutions. However they do WORK, and therein lies the rub--people tend to try something and then get all excited by the fact that they got good results. However, the results they normally get are no better than the results they would get without using the technique they're trying. I got one article from a guy who had tried water bath development, that seemed on the face of it like a decent article--he described his experiments rigorously, presented the results, and then had a nicely written section extolling the visual merits of his results. I wrote to him asking about his controls, and he said, "Controls?" So I got him to do the same experiment with controls--identical films developed with and without water bath development--and he concluded that there was no appreciable difference except that the water bath development was more uneven. Shel: If you plot the development activity of Rodinal (time relative to density), you'll see that it flatlines (or very close to it) at long development times. In other words, with Rodinal 1:100 you're not going to see very much difference at all between 15 minutes and 20 minutes development, or between 30 minutes and 40 minutes. Tom: if you experiment with minimal agitation, be sure to incorporate a test for evenness into your trials, and be sure to include a control negative developed to the same C.I. that _didn't_ get the "special" agitation. I'm pretty sure I know what you're going to conclude, but knock yourself out. Shel and Tom: The View Camera Store in Arizona has a very nice film testing service if you don't want to get into basic sensitometry on your own (or don't want to shell out for a densitometer). They send you films of the type you want to test exposed with step wedges, you develop them according to your chosen techniques, and then you send the negatives back to them and they plot the information for you. So in this experiment, you would get two films from them, you'd develop one according to your normal methods and one according to your experimental (I almost put that in quotes, but I'm trying not to be cyncial <g>) agitation techniques, and then you'd send the negs to them and they could tell you what the differences actually are. It's a nifty service and cheap compared to buying your own densitometer and coming up to speed on how to use it. For most of these techniques these days, what you're going to conclude is: a.) in an uncontrolled trial, you'll be amazed at the beauty of the results and be tempted to extol the specialness of the results in flowery terms; b.) in a controlled trial, you'll conclude that the results are pretty much indistinguishable from regular technique and not worth the trouble. A large number of these old techniques date from the days of thick-emulsion black-and-white films. Now that most films are thin-emulsioned (some extremely so, like Delta 100), the techniques are well-nigh useless. If you're going to go down this road, however, you might want to stick with the more old-fashioned films on the market such as Forte or Verichrome and stay away from the thin emulsions such as TMX. Just so that you refrain from adding to the web's vast storehouse of misinformation, resist the temptation to generalize from your results to other films and developers. In other words, if you find that negative density for Rodinal 1:100 doesn't change much with time past a certain point, don't postulate that the same will be true of HC-110 or Ilfotec HC; and if you find that minimal agitation makes a difference with APX 100, don't assume that similar results are achievable with the Delta films. Finally, be aware of two things: first, that many direct experiments that appear to be scientific, aren't; and second, most books on this subject (certainly Steve A.'s) are researched largely by reading other books. The trouble with that is that what was true for a 30 ASA thick-emulsion film in 1947 doesn't necessarily hold true for a modern emulsion. When you learn enough about this stuff to be able to trace the information back to where it originally came from, it's easier to see that much of the information you're being fed is simply no longer valid. --Mike - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Visit the PUG at http://pug.komkon.org.
