D-23, Microdol-X, D-76: Curves, Sulfite, etc.

[Ken Lee]

I have read that D-23 (not divided D-23, but D-23) is basically the same formula as Microdol-X. In these formulas, the main developing agent is Metol, while D-76 contains Metol and an additional developing agent, Hydroquinone.

They all rely on a considerable amount of Sodium Sulfite.

Do these developers produce an S-shaped densitometric curve with most films ? If so, why ? Does D-76 produce a more linear curve than D-23/Microdol ? If so, is it because of Hydroquinone ?

Compared to traditional films, are T-grain films less compatible with developers like these, which rely on Sodium Sulfite ?

Does the curve become more linear as theses developer are diluted (1:1, 1:3) ? Is that due to local exhaustion of developer ? If so, does that suggest that too much agitation reduces the compensating effect, and thus negate the benefit of dilution ?

Do these developers give lower film speed than other developers, which they trade for finer grain ?

I ask because I have been attracted to the simplicity of D-23, which has only 2 ingredients.

[Henry Ambrose]

If speed is not important I think you are correct. I've fooled around with D23 a bit and found it a nice developer. Its been a while though so I can only state a general impression.

[Drew Wiley]

The high amount of sulfite in D-23 acts like a silver solvent, so you sacrifice some
acutance; but this is a good choice for divided (2-tray) development. D76 gives better acutance. Curve shape at the top of the curve (the shoulder) depends a great
deal on the specific film. But with respect to the toe and middle part of the curve,
both of these tend to sag significantly. There are times when such a curve shape can be useful, but if you want a straighter line, HC-110, TMaxRS, or one of the pyro formulas would be a better choice. Straightness also depends on how far you expose
the film, and how to what level of contrast you develop it. With respect to 76, moderate dilution (1:1) does not seem to affect the curve shape a lot. I can't remember the effect with D23, since I haven't used it for a long time. An analogous developer which some folks like is Perceptol, which works well 1:1.

[BetterSense]

If speed is not important
That's the main reason I switched away from D23. I used to use replenished D23 pretty much exclusively until I started using Xtol and realized how much speed D23 was costing me. I still like it a lot...it was really in its prime in TX sunlight, on film that has been exposed 'generously'. It seemed to really tone down and smooth the highlights into something printable.

[Chuck P.]

But with respect to the toe and middle part of the curve,
both of these tend to sag significantly. There are times when such a curve shape can be useful, but if you want a straighter line, HC-110, TMaxRS, or one of the pyro formulas would be a better choice.

You're saying that with D-76, the toe and the middle of the curve sags significantly? I have not found that with D-76 and TMX as this combination is very linear in my tests.

I have longer toe and an upswept curve with TMX and HC-110.

[Oren Grad]

Does the curve become more linear as theses developer are diluted (1:1, 1:3) ? Is that due to local exhaustion of developer ? If so, does that suggest that too much agitation reduces the compensating effect, and thus negate the benefit of dilution ?

In principle a compensating effect should enhance any tendency toward a shoulder, thus making a curve less linear, not more.

[IanG]

This was Kodak's first Fine grain developer for 35mm stills camera use.

Eastman Kodak Research Fine Gran Developer 1927

For Fine grain. - A developer recommended by the Eastman Kodak Research Laboratories for use when images of specially fine grain are required is as follows:-

Metol . . . . . . . . . . . . . . . . . . 8 gr (2g)
Sodium Sulphite (anhyd) . . . . . . 400gr (100g)
Borax . . . . . . . . . . . . . . . . . . 8 gr (2g)
Water to . . . . . . . . . . . . . . . . 14 ozs *** (If US oz 1600ml - UK 1540ml)

The developer works more slowly than those of normal formula. - A.P., May 25, p. 504.

This seems to be one of the earliest published Fine Grain developer from Kodak. D76 was more specifically for motion picture processing (originally).

It's far more likely that the volume is US, particularly as the formula emanates from Rochester not Kodak Research, Harrow, but the difference is quite negligible. This formula pre-dates D76 and is quite similar to H76 and DK76 & DK76b, although more dilute.

Ian

[Ken Lee]

In principle a compensating effect should enhance any tendency toward a shoulder, thus making a curve less linear, not more.

Perhaps I have misunderstood. I thought that compensation gives a boost to shadow values, while leaving the high values less effected. This would lift the sagging toe of an S curve, no ?

[Ken Lee]

This was Kodak's first Fine grain developer for 35mm stills camera use.

Eastman Kodak Research Fine Gran Developer 1927

For Fine grain. - A developer recommended by the Eastman Kodak Research Laboratories for use when images of specially fine grain are required is as follows:-

Metol . . . . . . . . . . . . . . . . . . 8 gr (2g)
Sodium Sulphite (anhyd) . . . . . . 400gr (100g)
Borax . . . . . . . . . . . . . . . . . . 8 gr (2g)
Water to . . . . . . . . . . . . . . . . 14 ozs *** (If US oz 1600ml - UK 1540ml)

The developer works more slowly than those of normal formula. - A.P., May 25, p. 504.

This seems to be one of the earliest published Fine Grain developer from Kodak. D76 was more specifically for motion picture processing (originally).

It's far more likely that the volume is US, particularly as the formula emanates from Rochester not Kodak Research, Harrow, but the difference is quite negligible. This formula pre-dates D76 and is quite similar to H76 and DK76 & DK76b, although more dilute.

It appears that Anchell and Troop got things backwards: They write that D-23 was released by Kodak in 1941, as an improvement over D-76, which dates to 1927. They suggest that D-23 was introduced for the movie business.

I have wondered how a lower number (23) could supercede a higher one (76).

Which document do you quote for your formula ? Everywhere I have looked, D-23 is listed as containing 2 ingredients, as follows: 7.5 g Metol, 100g Sodium Sulfite, water to make 1 Liter.

(The 2-bath version - which I am not discussing - adds Sodium Metaborate (in the second bath). I am asking about D-23, not divided D-23. :)

[IanG]

Ken, I have various original Kodak publications with many of the formulae in, then also précis of various research papers published in magazines like the British Journal of Photography.

D23 & D25 were published at the same time in 1941, but it's part of the continuation of the earlier 1927 research.

Essentially D23 & D25 leave out the Borax so work at a lower pH, hence the need for more Metol, however the replenisher D25R contains Sodium Metaborate.

What's remarkable is just how many years Kodak spent getting from the early Fine Grain Developer (above) and D76 to D23/25 DK-20 and then Microdol.

I doubt Bill Troop was aware of the 1927 Kodak FG Developer when he wrote the FDC.

You can't read to much into Kodak's numbering system, you need to remember that often their early formulae came from companies they'd taken over or were clones of earlier formulae. After all both of Kodak's Research departments at Rochester (US) & Harrow (UK) were set up and led by Mees and his research staff from the UK company Wratten & Wainright.

It's possible that the initial work for D23 & D25 was done much earlier than 1941 because when Kodak had dichroic fogging issues with DK20 they went back to an earlier area of research for Microdol.

D76 itself is derived from an earlier Wellington & Ward Buffed Borax developer.

Ian

[BetterSense]

By the way, I never found that D23 resulted in 'softer' images from some supposed 'solvent' effect. I always got very sharp results from it, even comparing to other developers at high magnifications.

[Henry Ambrose]

Perhaps I have misunderstood. I thought that compensation gives a boost to shadow values, while leaving the high values less effected. This would lift the sagging toe of an S curve, no ?

I think of it the other way 'round. Compensation slows the building of excess density. So it lets the toe keep developing longer while not building density so rapidly. Kinda the same thing just thinking about it from different directions. You get more development at the bottom and gentler at the top.

A suggestion - write out on paper the formulas for D23 and D76, then maybe Divided D23 and Divided D76. Factor in dilutions to get to the actual working solution component ratios.

Also maybe mix some D23 without so much sulfite. Which starts to look like some other famous developer (D76) minus the hydroquinone.

[Drew Wiley]

Compensation builds up the toe. When you combine this with the added exposure
necessary for most films to do this well, and IF that particular film lacks a long
straight line, then you will push the film up onto the shoulder and acquire more of an S-curve. Again, it depends on the particular film. With an alkaline second tray
and D-23 and an old-style thick emulsion film, you could get effects similar to water
bath development, but with more control.

[Oren Grad]

Perhaps I have misunderstood. I thought that compensation gives a boost to shadow values, while leaving the high values less effected. This would lift the sagging toe of an S curve, no ?

Think about the postulated mechanism and about how compensating development is usually applied.

First, developer is said to become locally exhausted. This affects the most densely-exposed areas, though how far down the curve the effect goes will depend on the particulars of film, exposure, developer and dilution. If development time were unchanged, this would suppress highlights while leaving shadows unaffected, and tend to increase the strength of the shadows relative to highlights, but not affect their absolute density.

But second, together with diluting the developer, people tend to increase the developing time and/or add exposure to maintain a given overall density range. So the absolute density of the shadows will be increased. But if the maximum density for a given SBR is pinned at some fixed point, you have a zero-sum game in which a steeper slope at the bottom of the curve must be accompanied by a shallower slope somewhere further up the scale.

In reality, hardly anyone tests their materials and calibrates their processing conditions so rigorously that the maximum density is in fact absolutely fixed, so in practice there can be subtle changes all across the scale that are difficult to interpret with just casual eyeballing. Also, the effect of compensating development on modern films, short of extreme manipulations like extended stand develpment at very high dilutions, is probably modest anyway.

[Ken Lee]

Thank you all for the clarification.

Is there general consensus that these older Sulfite-based developers such as I have mentioned, give less linear curves, than Pyrocat and more modern commercial formulas such as HC-110, TMax ?

[Henry Ambrose]

Thank you all for the clarification.

Is there general consensus that these older Sulfite-based developers such as I have mentioned, give less linear curves, than Pyrocat and more modern commercial formulas such as HC-110, TMax ?

I don't know.

My take on the older developers was to see which combination would get the desired scene range on the negative and then the paper. I did plot a curve or two but really all I cared about was getting it all to print easy. Curves seem less important to me than "will it all fit on the paper without heroics".

I did decide that if all else failed I could happily use Divided D23 or David Vestal's Divided D76 or the same components mixed together into single bath. The only two things I didn't like was the speed loss (not that big a deal really) and the immediate mix/use situation. Regular or Divided D23 with TriX is really nice.

But Xtol solved both those things for me when all the questions were considered. Its easy to have pre-mixed doses ready to go and know that its the same now or in six months. That's not to talk you into Xtol but its where I got with this line of inquiry.

This is kinda like chocolate - if you like it there are lots of good kinds of chocolate and you will likely have a personal preference or two.

[Ken Lee]

It's all spelled out in The Darkroom Cookbook, by Stephen Anchell.

[Henry Ambrose]

And your conclusion is?

[Ken Lee]

Here are a few quotes that helped answer my line of inquiry:

"Strictly speaking, compensating developers are those that give proportionally full development to the shadow and middle values while limiting the degree of development in the high values." - pp. 52

"Developers are made up of four basic components:

* Developing agent
* Preservative, which slows the rate of developer oxidation
*Accelerator (or alkali) which energizes the developer
* Restrainer, which restricts the formation of excessive fog and/or slows the rate of development.

All four of these components are necessary for the development process to be successful. Often, however, one chemical will serve more than one function. For example, Sodium Sulfite is usually used as a preservative to prevent oxidation. In the film developing formula Kodak D-23 the large amount of Sodium Sulfite (100 grams) serves to create an environment sufficiently alkaline that the developing agent, Metol, can reduce the Silver Halide without an additional accelerator. As development proceeds, soluble Bromide is precipitated out of the film, acting as an effective restrainer. D-23 has only two chemicals - Metol and Sodium Sulfite - yet as a developer it has all four of the required components" - pp. 40

Anchell mentions that many general-purpose developers contain 2 developing agents, like D-76 which uses Metol and Hyrdoquinone: the two agents together, work better than one alone. This is known as Superadditivity. However....

"... it would seem that the best developers to use are those that exhibit superadditive characteristics. Most general-purpose developers fall into this category. However, there is a flip side. Most developers that utilize this effect tend to yield greater high-value density than those that rely on one developing agent. A developer of the semi-compensating type using either metol or pyro alone in a solution of relatively low pH, is capable of producing brilliant high values, full-scale mid-tones and shadows (e.g. Kodak D-23 and Kodak D-1, ABC Pyro, especially Edward Weston's variation)." - pp 42

"Kodak D-23
This is a semi-compensating developer that produces fine shadow values while retaining a high emulsion speed... Note: This developer produces negatives of speed and graininess comparable to Kodak D-76, without D-76's tendency to block highlights. " - pp. 150

So yes: D-76 (and similar general-purpose developers) give a comparatively S-shaped curve (compared to semi-compensating developers), because of Hyrdroquinone. But dilution can correct that: "general purpose developers... diluted 1:1 or more... provides additional highlight compensation without greatly increasing the development time and without causing loss of emulsion speed" - pp. 42

Finally:

"There is nothing that can compare to a full tonal scale black-and-white negative developed in Pyro. Negatives developed in Pyro exhibit exceptionally sharp edges and delicate highlight detail. That does not mean you cannot get superior results using conventional formulas, it simply means that a properly developed Pyro negative is as good as it gets" - pp. 68