Hydroquinone in Phenidone/Ascorbic acid developer

Photo Engineer said:

Ryuji is correct and the quote above expresses the essence of what happens in the tray with almost all current papers (Kodak, Ilford, Agfa, Fuji, etc).

Modern papers have a self limiting factor due to the high chloride content, and the nature of the incorporated addend and developing agents (if present). I have demonstrated this to myself over and over by observing what is stated in the above quote.

Some papers do not observe this behavior though and that is why we see a difference of opinion here among the posts. Papers made without some of the contrast control agents, developing agents, toners and etc will exhibit a different response in a given developer.

PE

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I'm learning something from this post. I confess that I haven't used a single-bath developer for at least twenty-five years of printing. It may well be that newer emulsions have changed sufficiently that the effects I described don't happen anymore. Back in the day, the print used to gain both contrast and density the longer it remained in the developer. That's one of the reasons I switched to divided developers, though the main reason was to eliminate the need for temperature controls since I was in Malaysia and found it difficult to keep my chemicals under 85F, even with a window-unit air conditioner.

I may try the single bath again and test my papers in it.

Larry

Peter De Smidt said:

My standard print developer for years has been Zone VI print developer, diluted 1+2. I believe that it's very similar to Dektol. (I use it because it's what I started with years ago, and I haven't had a good reason to switch.) My standard practice was to develop Ilford MG FB for 2 minutes at 70F. A while ago, though, I decided to speed match the various contrast grades gotten through my color head. To my surprise, I only achieved grade 3.5. In trying various things, I finally considered extending the development time. A four minute development time gave a maximum contrast grade of 4.5. More extended development didn't help.

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That story sounds like the developer is quite dissimilar from Dektol or any standard print developer of that type. Your developer is most likely low in pH, high in bromide, low in developing agent concentration, or perhaps combination of these. Ilford MG FB in fresh Dektol 1+2 will reach asymptotic curve within 2 minutes at 20C. Also, unless you used grade 4.5 or 5 filter, it is very strange that you even got grade 4.5 by longer development. Print emulsions are developed to completion, or until the sensitometric curve reaches asymptote. At that point no further development will buy you extra Dmax or contrast. Huge excess of development can only bring you troubles.

outofoptions said:

I have wondered about this. My experience is that if I hit the exposure right on the paper, I can leave it laying in the one bath developer a long time with no noticeable difference. Most folks seem to talk about paper as if it were film, but that is NOT MY EXPERIENCE AT ALL. Minimum time for maximum black exposure and you can cook that sucker for a long time. At least that is my experience.

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This is correct.

Intrinsic contrast of emulsion is often called "gamma infinity." This is the maximum value of gamma one can obtain by developing that emulsion for a very long time. This value depends on the developer but no pictorial emulsion developer can offer a drastically high gamma infinity from the same emulsion. That is, gamma infinity is rather a property of the emulsion to a large extent. (This is often not a quantity directly measured but it is a value obtained by extrapolation of experimental data.) Gamma infinity is determined by the statistical distribution (relative frequency) of sensitivity of individual grain. If an emulsion contains 1 part very fast emulsion, 1 part fast emulsion, 1 part medium speed emulsion, 1 part slow speed emulsion, wherein each of which has fairly high gamma infinity, the resulting emulsion will have much wider distribution than any of the ingredients alone, hence a lower gamma infinity. Once mixed and speed-frequency distribution is broadened, there is no way to reverse it (or to increase contrast).

Modern b&w camera negative emulsions typically blend 3 or more raw emulsions and have gamma infinity of 0.8 to 1.5 range. However, these emulsions are generally developed to much lower gamma (usually average gradient of 0.6 or so) by truncating the development way before the emulsions reach the gamma infinity. In the case of negatives, it is advantageous for several reasons.

On the other hand, enlarging paper emulsions do not receive quite the same degree of blending to lower the contrast, and the gamma infinity is a few times higher. These emulsions are developed until the gamma infinity is practically reached. There is no advantage in truncating development for prints.

This is the reason behind your observation.

Before c. 1985, the method used to make emulsions were quite different from that today. Well, I won't bore you with this story today. Also, in early decades of silver gelatin, negatives had higher contrast than today. Regardless of these, the basic idea is same. Even in very old darkroom instruction books, prints are developed to completion.

There is one exception to the statement I made above about there is no way to increase gamma infinity by changing the developer. Lith developer containing hydroquinone as the sole developing agent can increase gamma beyond gamma infinity achievable with ordinary developer. There's another class of modern high contrast developers containing hydrazine derivatives and optionally including amine contrast booster compounds. However, these come with considerable cost in image quality for pictorial purposes.