Basic developing question

Hi, I know this is a very basic question. Ok, with the same kind of developer, how different agitation and dilution affect the film, in terms of grain, sharpness, contrast, film speed and so on. I have been developing film myself, but still I am missing this part of the knowledge. Thanks.
-D

In short:

less agitation= less contrast, slightly more grain but better sharpness

Using a highly diluted ratio of developer will also give less contrast, slightly more pronounced grain but also better acutance especially when used in conjuntion with reduced agitation.

Would you please also explain why? Thanks.

Well basically when you use reduced agitation, local exhaustion of the developer takes place. Highlights or dense areas of the negative will always develop more quickly than thin/shadow areas. If agitation is reduced, then the dense highlights quickly exhaust the nearby developer while the shadow areas continue to develop and build density thus reducing the overall contrast of the negative. If you were to agitate more frequently, local exhaustion of the developer wouldn't take place and the highlights would continue to build much more density relative to the shadow areas. Using a more diluted developer works on a similar principle since a lower amount of developer leads to faster exhaustion when in contact with the highlight portions of the negative.
Using highly diluted developer also increases sharpness because it reduces the solvent components of a developer below workable levels. Most standard developers like D-76 use sodium sulphite (I believe thats the name) to dissolve the edges of grain and reduce its appearance. Unfortunately this reduces apparent sharpness. There is a ton of info about all of this that I haven't gone into. Complete books have been devoted to topics like this so its impossible for me to go into great detail on all of it. It is a fascinating topic once you read into it. I would recommend you try to find a copy of the "Film Developer's Cookbook" or Barry Thornton's "Edge of Darkness" Both do a good job of explaining why high resolution and fine grain negatives often produce subpar prints due to lack of visible sharpness. Both go into great detail about the questions you have asked.

Often, dilute development with semi-stand aggitation will increase film speed. Accutance will increase but at some point, edges will begin to look distorted. I did a lot of tri-x in p'cat with semi-stand and higher dillutions and images were very good at 30 minutes but not as good for an hour.

Daniel Lawton said:

Well basically when you use reduced agitation, local exhaustion of the developer takes place. Highlights or dense areas of the negative will always develop more quickly than thin/shadow areas. If agitation is reduced, then the dense highlights quickly exhaust the nearby developer while the shadow areas continue to develop and build density thus reducing the overall contrast of the negative. If you were to agitate more frequently, local exhaustion of the developer wouldn't take place and the highlights would continue to build much more density relative to the shadow areas. Using a more diluted developer works on a similar principle since a lower amount of developer leads to faster exhaustion when in contact with the highlight portions of the negative.
Using highly diluted developer also increases sharpness because it reduces the solvent components of a developer below workable levels. Most standard developers like D-76 use sodium sulphite (I believe thats the name) to dissolve the edges of grain and reduce its appearance. Unfortunately this reduces apparent sharpness. There is a ton of info about all of this that I haven't gone into. Complete books have been devoted to topics like this so its impossible for me to go into great detail on all of it. It is a fascinating topic once you read into it. I would recommend you try to find a copy of the "Film Developer's Cookbook" or Barry Thornton's "Edge of Darkness" Both do a good job of explaining why high resolution and fine grain negatives often produce subpar prints due to lack of visible sharpness. Both go into great detail about the questions you have asked.

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fhovie said:

Often, dilute development with semi-stand aggitation will increase film speed. Accutance will increase but at some point, edges will begin to look distorted. I did a lot of tri-x in p'cat with semi-stand and higher dillutions and images were very good at 30 minutes but not as good for an hour.

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Good point. There are some situations where you may no want to increase edge effects. (IE using higher speed film or push processing) You can go over the top with it. I gave unsharp making a try a little while back and the effect can look rather bizarre when you try to increase edge effects past a certain point. I've never experienced this using reduced agitation or highly diluted developer but I've also never really experimented with stand techniques in the 30min-1 hour mark nor have I tried any of these techniques with a 400 speed film.

Daniel Lawton said:

Using highly diluted developer also increases sharpness because it reduces the solvent components of a developer below workable levels. Most standard developers like D-76 use sodium sulphite (I believe thats the name) to dissolve the edges of grain and reduce its appearance.

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Note that this particular effect isn't universal because, although sodium sulfite is a common developer ingredient, it's not used in all developers. Rodinal doesn't have any, for instance. I seem to recall hearing somewhere that increased dilution actually reduces the graininess with Rodinal -- but I'm not positive of that. (My memory of this point is a bit foggy.)

srs5694 said:

Note that this particular effect isn't universal because, although sodium sulfite is a common developer ingredient, it's not used in all developers. Rodinal doesn't have any, for instance. I seem to recall hearing somewhere that increased dilution actually reduces the graininess with Rodinal -- but I'm not positive of that. (My memory of this point is a bit foggy.)

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Rodinal does contain some potassium sulfite, the MSDS states 30-40%. The amount present is not sufficient to act as a silver halide solvent.

Sodium or potassium sulfite appears in most all developers as it is needed for the developing agents to work. The only exception that readily comes to mind are the Gainer developers which depend on the presence of ascorbate ion instead.

Thanks for all the help!

Gerald, I've been using coffee developer with no sulfite of any kind for a couple years now -- just instant coffee and washing soda (to alkalize the solution). I get sharp negatives with a brown stain similar to pyrocat, leading me to believe that sulfite is not required for developers to work.

However, sulfite or another antioxidant *is* needed to preserve developing agents in stock solutions and aqueous concentrates. And don't forget that the 30-40% sulfite in Rodinal is before dilution; dilute 1:25, and you have 1.2-1.6%, already far too little to act as a grain solvent. Dilute 1:50, and you have 0.6-0.8%, and so forth. The only real reason to have the sulfite is to protect the p-aminophenol from oxidation in the concentrate -- and that works so well that the concentrate will keep for years in an opened bottle, as long as there's an excess of the p-aminophenol sulfonate precipitate over the potassium hydroxide alkali.

Hi,

Thanks for all the answers...

Besides, higer dilution will increase the grain, why is that? Will i loose film speed with higer dilution??

If I want to develop 2 120 rolls on one reel in one tank at the same time, is there a limit for the dilution?

Thanks again.

-D

dxphoto said:

. . . is there a limit for the dilution?

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Yes. You'll want to make sure that whatever dilution you use contains at least the minimum amount of developer required for the film area being developed. Check the developer's specs for this info.

dxphoto said:

Besides, higer dilution will increase the grain, why is that? Will i loose film speed with higer dilution??

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With most common developers, higher dilution means less solvent action, which makes the grain more visible (not necessarily bigger, but less soft edged). Sometimes this is barely detectable, if at all -- Rodinal gives little change in grain with dilution, because it has effectively no solvent action even at 1:25. Other times, it's a very large factor -- Microdol-X at 1:3 gives almost none of the "ultra fine grain" character it's known for when used at stock strength (but conversely also almost none of the speed loss).

Generally, diluting the developer and increasing development to give the same contrast will give more, not less film speed; at higher dilution, by the time the highlight areas are at the correct density, the shadows have received more development and gained density. The effect is small, however, anywhere from undetectable to about 1/3 stop in most cases (though very large changes, like using HC-110 Dilution G for 120 instead of Dilution B, and consequently greatly increasing time, can result in more significant speed increase).

As suggested, you need enough developing agent to avoid premature exhaustion with the amount of film you'll be developing; how much that is, however, varies from one manufacturer to another. Kodak recommends 100 ml of stock solution, minimum, per roll for D-76 and XTOL, 3 ml of concentrate per roll for HC-110. Ilford says, within their recommended dilutions, as long as it covers the film it's enough. Agfa has recommended 10 ml Rodinal per roll for a long time, and folks who like high dilutions (like 1:100 and higher) have ignored the advice for almost as long, and gotten good results with 1:100 and even up to 1:300 for some specialized applications (like microfilm) using no additional working solution volume.

If you want to use (for instance) D-76 1+3 for 35 mm, you won't fit 400 ml of working solution in a single reel tank; the recommendation in such circumstances is to use a two-reel tank with a single reel loaded, and enough working solution to supply the minimum.