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Re: Jobo atl3From: dickburk@ix.netcom.com (Richard Knoppow) "Darkroom User" <Darkroom.User.6a97369@photobanter.com> wrote in message news:Darkroom.User.6a97369@photobanter.com...
I think it is always interesting to experiment and learn. There is a definite effect of highlight compression when using a staining developer with variable contrast printing materials. Its quite measureable but may not be worth doing or may not be desirable for all images. The newer pyro formulas, like PMK are attempts to overcome some of the faults of the classical formulas, mostly that they tended to be grainy and somewhat unpredictable. The grain comes mainly from being active, most of these formulas use sodium carbonate or some equivalent as accelerators. They were necessary for the films which were contemporary with the developer. they work with newer films, especially when diluted more than the original instructions indicate. Formulas like the late ABC Pyro as published by Kodak, Ansco, and others, is fairly long lived in stock solutions and has relatively constant activity. Kodak D-7 is a Pyro-Metol formula with somewhat longer life in a tank or tray than ABC. There are a lot of variations. In my list are some special formulas including Kodak's version intended to maximize the stain image. Note that some users of PMK or Rolo Pyro suggest an after-bath in the developer to maximize the stain. What that does is to produce an overall stain, which is _not_ desirable rather than the imagewise stain which is what you want. A properly developed pyro negative should have little or no stain in the clear portions but a noticable yellow, greenish, or brownish stain following the image. The tanning is visible as a relief image on the dry film when held so that light reflects from the emulsion surface. Tanning developers were highly developed for use in producing the relief images used in the Kodak Dye Transfer process and Flexichrome process, each of which made use of the tanning to make parts of the emulsion more resistant to being removed by hot water. When "developed" by rinsing in the water the remaining emulsion followed the iamge exactly and could be used for absorbing dyes either for direct use (Flexichrome) or for transfer to a support paper in a process similar to lithography. An earlier version of the dye transfer process, called the Eastman Wash-Off Relief process used a different method of differential hardening, namely a bichromate process similar to that used for Carbon/Carbro. If you are interested in these old processes do a Google search for "alternative processes". Most are still practiced and can produce beatiful results. However, I suggest for someone starting out to make life simpler by using well-established packaged materials. Once you get control of the overall process of development and printing you can try experimenting with mix your own chemistry. Most of it is not difficult to do. There are NO magic developers but some have definite personalities which can make them interesting. Pyro is of historical importance, it was the first organic reducing agent to be discovered. I would not discourage anyone from trying it out but work with something more modern first. At this time probably the closest thing to an "optimum" developer is Kodak Xtol. Next choice is D-76, which is close to optimum for nearly anything and is perfectly reliable. After having used a lot of print developers I have gone back to plain old Dektol. The published formula D-72 is about the same stuff. Ilford makes an equivalent. Ilford Bromophen is a Dektol type developer that uses Phenidone in place of Metol. It is better for you if you are sensitive to Metol, which some people are and tends to give more neutral colored images with some materials. It is perfectly satisfactory. There are about a zillion print developer formulas that go to show simply how imprecise one can be in formulating:-) There is not much difference from one to another. As far as warm vs cold tone, that is mostly a property of the emulsion. While it is influenced by the developer its mainly established by the paper. Developers can have some influence on toning but that is often related to the amount of bromide in them or other variations that can be had by varying around a standard formula. One of the biggest differences between B&W and color photography is the lack of standardization in B&W. Color processing is very tighly specified and controlled and, while some variation is possible, the range of variation within which satisfactory Coloring Pictures">color can be obtained are fairly limited. -- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com
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