Response to Effect of HIGH dilutions HC-110 Tri-X?

Ansel Adams in "The Negative" describes the use of HC-110 at 1:120 dilution. The minimal agitation is to enhance the compensating effect in the highlights. You could expect more edge effects and more grain. The text below is copied from one of Richard Knoppow's erudite answers to a similar question in rec.photo.darkroom. I hope that it is in order for it to be pasted here.

"I think the chemical rule of thumb is that time is increased at about the square root of the dilution. e.g. diluting 1:1 should take about 1.4 times as long to reach the same contrast. Some effects of dilution depend on the formulation of the developer. High-sulfite developers may produce slight additional film speed when diluted because of the lowered concentration of Sulfite. They will also be a little grainier. Highly active developers may exhibit just the reverse effects. Many developers will produce increased "edge effects" due to local exhaustion of the developing agents and build up of reaction products at the interfaces of high and low density areas. Again, the lowered sulfite contcenration will tend to cause this since part of the function of the sulfite is to regenerate the reaction procucts. Diluted developers, again because of lower sulfite concentration, will have shorter lifetime than full-strength solutions since the sulfite will be less able to protect the reducing agents from oxidation from dissolved air or air at the surfaces. Edge effects are also partially controlled by the amount of solution which can be held by the gelatin emulsion. Modern films have rather thin emulsion layers so are more likely to show the effects of diluted developer or lack of agitation. A developer like D-76 will have very similar characteristics at 1:1 as it has at full strength but at 1:3 will start exhibiting very strong edge effects with many films. If a developer is diluted enough it may start to run into problems with general exhaustion of the reducing agents. Such a developer may produce very low contrast and low densities even with extended development times. The localized effect of such exhastion will be exagerated "compensation" which is actually sometimes useful." --- Richard Knoppow Los Angeles, Ca. dickburk@ix.netcom.com

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