Cold Developersgreenspun.com : LUSENET : Large format photography : One Thread
There are many methods for controlling the range of densities on a black and white negative. For example, highly diluted 'pre-developers' used in conjunction with development in normal concentration.
I was thinking that, since the rate of chemical reaction between the silver on the film and the developer is dependent on the temperature of the developer as well as concentration and time, one should be able to control the magnitude of development in shadow areas relative to highlight areas through a period of development in a cold developer solution. Development in a solution at normal temperature may be used to bring up highlight areas after shadows have come to full development in the cold solution.
I have never tried this and there may be no advantage to doing so. I thought I'd ask about it because someone out there may have tried it. Any thoughts on the matter are appreciated.
-- Jason Kefover (firstname.lastname@example.org), August 11, 2000
A cold developer will slow development in the shadows and highlights to the same degree, as will using a shorter time. Dilute developers can give highlight compensation, but a cold developer will not.
-- William Marderness (email@example.com), August 11, 2000.
"A cold developer will slow development in the shadows and highlights to the same degree, as will using a shorter time." This is true only if the activation energy for the chemical reactions of developing the shawdows and highlights is equivalent. Does anyone know if this is true? (Warning, potentially irrelevant credential info follows: I'm a Ph.D. physical organic chemical whose dissertation centered on elucidating reaction mechanisms.)
-- Chris Hawkins (firstname.lastname@example.org), August 11, 2000.
Try it and see. Then report back.
-- Bill Mitchell (email@example.com), August 11, 2000.
I am under the impression that using a shorter development time does not reduce densities to the same degree in shadows and highlights. It seems to me that the Zone System depends on greater reduction in highlight areas as opposed to shadow areas with reduced development time and greater build-up up density in highlights as opposed to shadows with increased development time. I know that shadows come to full development long before highlight areas.
I am also under the impression that the activation energy required in shadow areas is less than that for highlights. [Disclaimer: I may be way off here, the truth is, I don't know this to be a fact.] But, it makes sense to me that this would be the case.
-- Jason Kefover (firstname.lastname@example.org), August 11, 2000.
No scientific evidence (at least, of a rigorous naturee) to back this up. But I believe that rate of development is generally slowed uniformly (at the least, any difference that is there does not seem useful in control terms). So, at the risk of generalizing and ignoring other interactions in the process, reducing time and temperature will affect shadows and highlights proportionally. In my opinion, dilution also reduces activity proportionally across shadows and highlights. However, some compensation is possible with dilution because of the barrier in the form of the emulsion which leads to local increases in development byproducts (note: obviously developer formulation is a critical factor in this generalization - a lith developer, for e.g., will increase contrast locally since the reaction byproducts increase activity). However, the biggest uses of dilution, in my experience, is not the slight compensation it confers from the emulsion barrier slowing diffusion. By slowing the rate of development (viz., increasing time), it allows one to use much lower levels of agitation (once every three minutes instead of every minute) and this compensation is much greater than any inherent compensation due to dilution itself. Caveats: These conclusions reached by testing Arista 125 with various dilution and agitation patterns in HC110. Make of it what you will. Cheers. DJ
-- N Dhananjay (email@example.com), August 11, 2000.
Maybe I did not say it right above. What I meant was making a developer colder is often the same as making the time shorter. A lower temperature slows down the process. If the developer contains hydroquinone and metol, I have heard that the activity of these agents is not exactly the same at different temperatures, so contrast may vary a bit with some developers.
-- William Marderness (firstname.lastname@example.org), August 11, 2000.
Various developing agents and other agents (such as sodium sulfite) have different sensitivities to temperature. For example, if I remember right, hydroquinine becomes completely ineffective at lower temperatures.
Thus changing the temperature far from normal is, in effect, reformulating your developer. And, of course, this can dramatically change your characteristic curve.
-- Charlie Strack (email@example.com), August 11, 2000.
A lot of speculation!, Like the man said, TRY IT! And let us know how it comes out. Pat
-- pat krentz (firstname.lastname@example.org), August 11, 2000.
All I know is that with paper developer, using really cold developer after the basic image has come up will make for very easy, repeatable and controllable solarized prints.
-- Dan Smith (email@example.com), August 12, 2000.
The developer works at a constant rate depending on temperature. The reason that a colder temperature would not work as a compensating factor is because of the nature of the siver within the emulsion. The sivler halides in the emulsion at exposure are energized in direct relation to how much light hit them. The shadow values have the least energy imparted to them. Few silver halide crystals were hit. The silver halides in the highlights were activated to a much greater extent. When the film is emersed in the developer and the emulsion saturated the less energized(fewer silver halides struck) areas develope at the same rate as the highlights. But the shadow areas quickly become completely developed. There is no more silver to convert. The highlights continue to develope. As the midtones develope out and all the energized silver is converted those areas are finished and only the areas with the most silver energized continues to develope until those areas also finish developing with no more silver to convert. So the colder temps only slow down the entire process at the same rate until the difference is great enough to inhibit some developers from working at all. Raising the temps works in the opposite direction. But the same steps occur just at a faster rate. The idea behind compensating developers or water bath systems is that the emulsion holds only a certain amount of chems and these are exhausted at a certain rate. So the silver is still converted at the same rate but the highlight densities use all the developer just as quickly exhausting it. The act of agitation renews the developer in all areas but the shadows have no silver left to convert so all that is left is the conversion of the silver in the higher densities. Agitation and time are the only two variables left. Don't agitate a lot and you can control the conversion of silver at a steady rate. Leave it in longer and you get the same thing. James
-- james (firstname.lastname@example.org), August 12, 2000.