Ilford processing times (Pan F)
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From: Richard Knoppow on 24 Jul 2010 03:05 "David Nebenzahl" <nobody(a)but.us.chickens> wrote in message news:4c476980$0$2401$822641b3(a)news.adtechcomputers.com... > After my recent success with TMX, I delved into my > freezerful of film and pulled out a roll of Pan F I want > to shoot. But I'm a bit mystified by the enclosed > processing instructions. > > Was thinking of using D-76, and they have times for both > this and ID-11 (same times, since the same developer, > except that they list ID-11 at 1+1 but not D-76, though I > assume I can also dilute it). But they show the same times > for both ISO 25 and 50 exposure. Can this be correct? > Other developers show different times for the two speeds. > > They also show times for Perceptol, but not Microdol-X. > Richard K., you said these developers were equivalent: > would you use the same times for both of these? The > Humumgous Massive Really Really Big Dev Chart > (http://www.digitaltruth.com/devchart.php) shows different > times for these (9 min. for Perceptol vs 12 min. for > Microdol; should I just use their recommendations? > You will notice that Kodak also rates T-Max 100 and 400 at double speed with normal development. The differece between the two exposure indices is a difference in overall density and in shadow detail, the contrast remains the same. When the ASA system of speeds was introduced in 1943 it included a safety factor of two so that all film speeds were half the value actually determined by the test method. For some reason this was thought to be a good idea even though the research at Kodak from which the standard was adopted was intended to find the _minimum_ exposure possible for good tonal rendition. This was because film is somewhat less grainy and somewhat sharper for thin images. Nontheless, the lower speeds were recommended. I think the reason is that Kodak, in particular, wanted to insure amateur users would get a printable image and overexposure does less damage than underexposure. In 1958 when the ASA adopted a modification of the then new DIN standard, which was much easier to measure than the minimum gradient method previously used, they also dropped the fudge factor and all film speeds were doubled! That put the manufacturers of "magic" speed increasing developers out of business. They all knew and counted on the fact that all films were actually double the speed given by the ASA. Kodak actually talks about this in the introduction to the film booklet included in the _Kodak Reference Handbook_ but its obscured by recommending increased speed only to essentially professionals. In any case many photographers find that increasing exposure from that given by the ISO speed often results in better shadow rendition and, with modern thin-emulsion film has little effect on grain or sharpness. -- -- Richard Knoppow Los Angeles, CA, USA dickburk(a)ix.netcom.com |