Developer Dilution & Developing Time Compensation Effect on BW Negative Films

(Sorry for the awkward thread title but I couldn't think of a more clear way which is still short enough to use as a thread title to state my question .)

For, quote and unquote, normal film development, when we use a more diluted developer we would compensate by using a longer development time . E.g., For Tri-X at 20°C, in stock D76 the development time is about 7', and when we use 1+1 dilution the development time is about 10'. I wonder how close the results of the two different dilution-time combinations would be. Are they close enough to be considered "equivalent" or are they different enough that we should be very careful when choosing the combination to use? What does your experience tell you?

Essentially they are the same result, but there are differences.

In general the stock solution will be slightly smoother, whereas the diluted 1+1 solution will give you slightly more visible grain. 1+3 is another variation which gives a slightly different look again.

At the end of the day, all of the advertised (by film manufacturers) developer dilutions and times will give you very close but not quite identical results.

My personal usage of D76, which has been continuous for decades, is 1+1, but sometimes (around 30 years ago) I would have some films developed by a professional lab which was D76 straight, but being continuously replenished based on the amount of film that went through.

Comparing the professional lab films with my own, one really had to look to see the difference.

Others will have different experiences, these are mine.

To elaborate on Mick's reply:

D-76 stock (full strength) has a high concentration of sodium sulfite, which acts as a silver solvent, dissolving and redepositing silver on the developing grains. This results in "finer," but less well-defined grain. At 1+1, D-76 has a lower concentration of sulfite, and the grain is therefore more pronounced, but "sharper."

With other developers that don't exhibit this kind of silver-solvent activity at full-strength, diluting often makes no real difference as long as the development time is proportionally extended and agitation is consistent and often.

However, many use dilute developers and longer periods between agitations to maximize compensation and edge effects. When the agitation is less frequent and the developer dilute enough, it exhausts in the areas of higher density (i.e., more active development) before the next agitation cycle. This results in those areas receiving proportionally less development resulting in less-developed highlights in relation to the mid-tones and shadows. This is the compensating effect.

Also, with many developers and compensating-style developing, the developer in the higher-density areas exhausts and makes bromide as a by-product. This bleeds over just a tiny bit into adjacent lower-density areas, making a small line of less density along the interface. Simultaneously, a bit of the more-active developer in the low-density area will bleed over into the higher-density areas, making a small line of more density on that side of the interface. The resulting double-line of high/low density between a very high and very low-density area can be quite pronounced and is called a Mackie line. It lends a look of extra definitions and sharpness in many cases and some of us strive to maximize this effect just for that characteristic look. Dilution of the developer and agitation frequency play important roles in this process.

Also, in the past I have found that a more-dilute developer and longer developing times allow me to achieve more contrast than with a more concentrated developer and extended development time. This, I believe, is due to the activity of the more-concentrated developer causing increased base fog with extended development times, which doesn't seem to be such an issue with a more dilute developer and even longer development times. For example, I could get significantly more contrast from a Tri-X negative with HC-110 at 1+63 and very long times than I could with the same developer at 1+31 and the appropriately long time for N+2 development.

Hope this helps,

Doremus

I don't know the science on this, and don't need or want to know it, but I always preferred D76 in a stock solution. This is all personal taste of course. You get a smoother image, and just beautiful tones w/ Tri-X. It's plenty sharp, but the 1+1 is a little sharper. You lose some of the stock solution's tones as well.

None of this difference is in your face, it can be subtle if you keep the agitations gentle. Hard agitations always gave me a little more contrast.

The difference between 12 minutes stock, and 17 minutes in D-76 1:1 is negligible. Tonality and speed are very close.

My guess is that the mid-tone areas would mostly be similar. My concern is mostly on the highlight and shadow areas, especially the highlights. My thinking is that a less rapid development in the HL area with a more diluted developer over a longer time will produce more details than a more rapid development with a more concentrated developer over a shorter time. What do you think, or have you experienced?

(I know I can, of course, do a bunch of tests myself, but I don't have the budget and time — not to mention that I don't have a densitometer.)

In general, I'd expect prolonged development with high dilution (especially if agitation is limited) to reduce contrast in the highlights, but also to reduce overall highlight density -- that is, it would act as a compression for values above Zone IV or so. This is because there's more exposed halide to develop in those areas, so local exhaustion of the developer comes into play. This doesn't occur in the shadow areas, however, because there's less exposed halide there; the result can be an expansion of shadows (even a true speed gain), combined with compression of highlights; effectively introducing some shouldering in the H+D curve.