Basic developement controls

I want to make an basic list for development controls. Please tell me if all starting points below are correct, assuming correct exposure:

Developing time:
- increasing time: higher contrast, bigger overall density;
- decreasing time: lower contrast, lower overall density;

This happens because shadows are developed early and fast, and highlights/mid-tones are developed later and keep going. So increasing contrast will make highlights/mid-tones more dense.


Developer dilution:
- high dilution, lower contrast;
- low dilution, higher contrast;
- for some developers, lower dilution -> more accutance


Why? I assume because low dilution gives more power to the developer which will act more on highlights/mid tones, as with above developing time

Keeping the film in water without agitation 3-4 minutes after development (no stop bath) will increase accutance (water has a mild compensatory effect). Tested, I did not noticed any difference.

For some developers, higher dilution gives higher acutance. Examples are D-76 and D-23, This is because the silver solvancy and fine-grain mechanisms are reduced by dilution.

For some developers, like D-23, compensating action is increased by dilution. Higher temperature increases development (for a given development time) and therefore increases contrast and density. Lower temperature does the opposite. But if temperature is reduced too much (below about 62F fior most developers) some developing agents more or less stop working, and the developer characteristics change.

VladimirC said:

... happens because shadows are developed early and fast, and highlights/mid-tones are developed later and keep going...

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Shadows build up little density, slowly. They do not do much more when you develop them longer.

@nworth: No, we assume temperature = 20C. As with temperature time will need to be modified for the same negative, I don't want variables mentioned here to effect each other, as it will complicate.

@Bill: Exactly. If you develop longer shadows will not change much, highlights/mid tones will build up, right ? That means high-contrast, this is what I wanted to say.

Negative density is determined by exposure and contrast is determined by development. No amount of development can create detail where none exist.

Gerald C Koch said:

Negative density is determined by exposure and contrast is determined by development. No amount of development can create detail where none exist.

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Yes, of course. But a small amount of development can decrease detail, not revealing it all. And more, detail is not everything. Gray 30% is one thing, gray 60% is another thing, even if we're talking about two squares.

Imagine a picture with a rectangle cut in two, one side darker, one lighter. With development you can decrease/increase contrast (difference between the two sides). Now extrapolate.

VladimirC,

I'm sorry but I don't fully understand your comment. Of course if a negative is underdeveloped it will lack detail particularly in the shadows. But if a negative is underexposed then no amount of development can create detail. Although a lot of past developer manufacturers made lots of money claiming their developers increased speed.

I suspect we are saying pretty much saying the same thing.

Yes, indeed we are.

I still do not know for sure why increase dilution gives lower contrast, is what I've said in my first post ?