I did not know that one of my patents was referenced in Haist, as the book was being edited at about the time my first patent issued. I was one of the editors of the book too. Shame on me!
Anyhow, staining developers create a dye image and just like any dye image there are two factors present due to these dye clouds. First, there is image smear due to the clouds being diffuse, but second is the introduction of the grain caused by the dye clouds. Sulfite in the developer can reduce the image smear, but might either eliminate dye formation totally or concentrate the dye that does form, and create more grain or at least no change in grain. Just some thoughts here.
As for tanning developers, they react by differential hardening of an emulsion at edges, thus creating enhanced edge effects. They too are affected by Sulfite, but in addition they differ from film to film due to hardening differences in film. If a film is very hard (Kodak, Fuji, Ilford), then the film is very weakly affected by a tanning developer. Ideally, a fully unhardened film should be used to maximize tanning effects. Now, a staining developer might give a tanning effect because the staining reaction can have some hardening effects and in addition, the dye can bulk up the emulsion and give the effect of tanning. This took place in Kodachrome and thus you see a relief image caused by the dye that forms and takes up more space than the original coating. This effect increases sharpness due to the boundary.
Umut, AFAIK, the sale of unhardened films intended for forming relief images ended with the sale of Dye Transfer materials. The closest at the present time is the Matrix film work alike formulated by Jim Browning and sold through EFKE.
Interesting. It is generally assumed (or stated/claimed) low-sulfite Pyrogallol/Catechol B&W film developers simlutaneously tan and stain imagewise. Tanning and staining actions are typically thought of as essentially one "process".
Originally Posted by Photo Engineer
So, concerning these developers, is it generally fair to say the sharpness typically associated with them has mostly to do with edge effects and more pronounced graininess (relative to a typical solvent developer)? It would seem resolution and traditional acutance would at best be no better than a general purpose developer - in fact may be worse due to dye spread.
Further to this, with well hardened film, if tanning effects are limited, is dye spreading or image smear also limited? Or do we just get dye spreading without enhanced edge effects?
It is interesting that sulfite can reduce image smear. Would this be an effective argument for finding a balance between maximum imagewise stain and image precision when formulating a staining developer? I don't get the sense that is the usual approach. Most formulations seem to be aimed at using the lowest practical amount of sulfite possible to stabilize the formula, in an effort to maximize imagewise stain.
Michael, you have asked too many questions for any possible answer here. This would be a week of lectures or some such in a course on developer design! :)
Ok, Sulfite is used as a preservative in developers. It is oxidized by air. Thus, it is not the primary agent to prevent anything regarding the image. In fact, D76 only "survives" as a solvent developer by virtue of having such an excess of Sulfite present. That is a gross oversimplification, but it will suffice here. Actually, the real protectors are in the color emulsions.
So, that said, any effort to use Sulfite in a staining developer is doomed by being subject to severe variability.
Ok, so the reaction is Hq or any of the staining developers -> Q and Q + gelatin = extra hard gelatin with edge separation or tanned image, depending on use and film. If Sulfite is present, then Q + Sulfite = HQMS (Used in the E6 process as the main B&W developing agent). In this case, the Q can polymerize to give us colored byproducts (stain) or hardness (imagewise hardness) or both. So, one developer can serve two purposes.
You asked earlier if you could see a Kodak test so, in the article in Image see figures 3 and 4. These are a close approximation of what I get, but imagine it being done at 7 or more stop increments.
Umut, I have no idea about those heat sensitive emulsions, but I do know that Kodak sold a dye heat transferred print system for their digital cameras.
A question now about agitation and the formation of edge effects with general purpose developers. Of course generalizations are difficult if not impossible, but still.
Anchell/Troop take the view that generally speaking a rest period of 30s between agitation cycles is too short. One minute is the minimum, and longer rest periods result in greater edge effects, and continuous agitation essentially prevents them altogether. On the other hand, edge effects are supposed to be the product of diffusion within the emulsion layer. In Richard Henry's tests, he found continuous agitation, 20 second rest intervals and 1 minute rest intervals produced the same edge effects. Unfortunately he does not go into much more detail on that, and he did not investigate longer rest periods (3 minutes is a common recommendation for maximizing edge effects with non-solvent compensating developers).
What are your thoughts on this? Clearly many variables are involved, but are edge effects as sensitive to agitation as we assume they are?
That is certainly interesting...
Originally Posted by Michael R 1974
I did investigate the difference between 3-min agitation intervals and stand development:
Nowadays I use Don Cardwell's recommendation from his reply.