does pH affect grain and film speed?

[alanrockwood]

Question: If I have two developers that are the same except for pH, and I develop two samples of film of the same film type and same image, and I develop each film to the same degree of development, does pH affect the graininess or film speed?

 

[Bill Burk]

I look forward to real knowledgeable responses.
My guess is, everything else being the same, you would see more development activity with higher pH and less with lower pH... so the impact would be on development time.
So the end-result if you kept development time the same is that you would get thinner negatives with lower pH and more dense negatives with higher pH.

 

[alanrockwood]

I look forward to real knowledgeable responses.
My guess is, everything else being the same, you would see more development activity with higher pH and less with lower pH... so the impact would be on development time.
So the end-result if you kept development time the same is that you would get thinner negatives with lower pH and more dense negatives with higher pH.

To clarify my question, I was thinking in terms of developing to the same density, not the same development time.

 

[Raghu Kuvempunagar]

Hi Alan,

You did some experiments lowering the pH of HC-110 sometime ago. Did you get a chance to compare the reduced pH working solution with normal working solution at your chosen dilution from the point of view of grain and sharpness?

 

[alanrockwood]

Hi Alan,

You did some experiments lowering the pH of HC-110 sometime ago. Did you get a chance to compare the reduced pH working solution with normal working solution at your chosen dilution from the point of view of grain and sharpness?

Thanks for noticing that work. I have not had a chance to compare grain and sharpness. However, that is part of the reason I asked the question in this thread, i.e. to see if there are some rules of thumb that might apply.

 

[Ian Grant]

Well think of how the pH of D23 is lowered by adding Metabisulphite to make D25. Lowering the pH reduces developer activity needing a longer development time and grain is finer.

With Microphen Part A contains a small amount of Metabisulphite as a preservative, so the production formula the buffering differs marginally from ID-68 (which contains no Metabisulphite), to maintain the pH.

Another example is the increased activity of DK76 compared to D76 because the pH is higher with Sodium Metaborate.

Ian

 

[Ian Grant]

I should have added higher pH doesn't necessarily increase grain, dilution also plays a big part. So Rodinal which has probably the highest pH of any fine grain developer is an exception, however note that Rodinal produces finer grain with certain films like the original Agfa APX100, Tmax & Delta 100, but not all other films.

Ian

 

[RalphLambrecht]

I should have added higher pH doesn't necessarily increase grain, dilution also plays a big part. So Rodinal which has probably the highest pH of any fine grain developer is an exception, however note that Rodinal produces finer grain with certain films like the original Agfa APX100, Tmax & Delta 100, but not all other films.

Ian

Yes;I was very surprised how fine of a grain I got from Rodinal 1+50 and APX100;35mm could easily be enlarged to 12*16

 

[alanrockwood]

Well think of how the pH of D23 is lowered by adding Metabisulphite to make D25. Lowering the pH reduces developer activity needing a longer development time and grain is finer.

With Microphen Part A contains a small amount of Metabisulphite as a preservative, so the production formula the buffering differs marginally from ID-68 (which contains no Metabisulphite), to maintain the pH.

Another example is the increased activity of DK76 compared to D76 because the pH is higher with Sodium Metaborate.

Ian

Very interesting. The complication in interpreting those results is that by adding metabisulphite one is changing not just the pH but also the sulfite concentration, so there are two variables being changed, and sulfite is a known grain reduction agent due to its solvent action on silver and silver halide.

 

[Ian Grant]

Very interesting. The complication in interpreting those results is that by adding metabisulphite one is changing not just the pH but also the sulfite concentration, so there are two variables being changed, and sulfite is a known grain reduction agent due to its solvent action on silver and silver halide.

In the commercial production formula for Microphen the level of Sulphite is adjusted so that when the Metabisulphite decomposes shortly after mixing there's then the correct 85g/l Sulphite and the correct pH. Ilford use a very small amount of Metabisulphite in Preceptol and Bromophen for the same reason, so did Kodak at one time in some of their developers.

Ian

 

[Ian Grant]

Yes;I was very surprised how fine of a grain I got from Rodinal 1+50 and APX100;35mm could easily be enlarged to 12*16

Some people won't believe just how fine the grain can be with some films and Rodinal, but then it was Agfa's recommended developer for AP100 and later APX100. I remember the first film I shot with my Leica M3 & 50 Summicron it was Agfa AP100 developed in Rodinal and the quality was stunning.

Ian

 

[alanrockwood]

Some people won't believe just how fine the grain can be with some films and Rodinal, but then it was Agfa's recommended developer for AP100 and later APX100. I remember the first film I shot with my Leica M3 & 50 Summicron it was Agfa AP100 developed in Rodinal and the quality was stunning.

Ian

I wonder if Agfa purposely formulated APX100 to perform well in Rodinal, given the fact that Rodinal was one of their important products.

 

[Alan Johnson]

Question: If I have two developers that are the same except for pH, and I develop two samples of film of the same film type and same image, and I develop each film to the same degree of development, does pH affect the graininess or film speed?

See p119 etc. Also note that increasing the pH increases the rate of development but has less effect on the rate of deposition of finely divided silver and it is partly the finely divided silver that makes the film appear less grainy.
https://babel.hathitrust.org/cgi/pt?id=mdp.39015016032883;view=2up;seq=130

 

[Photo Engineer]

Use of Metabisulfite to adjust the pH varies the final level of Sulfite in the developer. Thus you vary the "Sulfite" effect on grain and sharpness. This is a poor way to vary pH for testing these qualities as you are influencing your result by the additive as well as the pH. It is best to use KOH or NaOH for making things more basic, and H2SO4 or HOAC to move to the acidic side.

As for pH effects on grain (and sharpness), pH does change the form of the developed silver. It can change from filaments to tablets or vice versa. This cannot be predicted in advance, as it is due to the emulsion and the developing agents. How the grain and sharpness are affected also depends on many other factors such as Iodide content of the film.

PE

 

[Ian Grant]

Use of Metabisulfite to adjust the pH varies the final level of Sulfite in the developer. Thus you vary the "Sulfite" effect on grain and sharpness. This is a poor way to vary pH for testing these qualities as you are influencing your result by the additive as well as the pH. It is best to use KOH or NaOH for making things more basic, and H2SO4 or HOAC to move to the acidic side.

As for pH effects on grain (and sharpness), pH does change the form of the developed silver. It can change from filaments to tablets or vice versa. This cannot be predicted in advance, as it is due to the emulsion and the developing agents. How the grain and sharpness are affected also depends on many other factors such as Iodide content of the film.

PE

Well it,was Henn & Crabtree who used Metabisulphite in D25. Although the formula was published by Eastman Kodak Research it was never sold commercially. There's a big issue of whether you use Bisulphite as Henn & Crabtree's formulae or Metabisulphite they aren't the same and the purity of Bisulphite can be quite varied, and this will have a large effect on the pH. Sodium Bisulphite varies between 58-99% Metabisulphte and 42-1% Bisulphite, Metabisulphite, Metabisulphite is usually 99-100%, JT Baker manufacture both.

Ian

 

[Photo Engineer]

I think my comment was oversimplified. In this type of experiment, where you are using Sulfite, Bisulfite or Metabisulfite to attain varying pH values, the amount of solvent will vary and thus the effects on image structure will vary. If you want to experiment, you should select one level of these compounds, and adjust pH by other means! I do not dispute the effect of these compounds having an effect on image structure that varies with concentration. And, purity is an essential part of photographic solution design.

You can also vary the level of these compounds and keep the pH constant.

Thus you can run a factorial experiment with pH and solvent and solvent type as variables looking at image structure.

PE

 

[alanrockwood]

I may have answered part of my question, at least for a special case. Last night I did some testing on Fomapan 400 using my witch's brew of modified HC110 (1 part HC110 syrup, 2 parts common 5% white vinegar, 13 parts of water.) Using my densitometer, I found a film speed of 100, which is two stops below box speed. Rumor has it that the true film speed of Fomapan 400 is closer to 200, i.e. one stop below box speed, but in this case I was getting two stops below box speed, so it is suggestive that, at least for this film, lowering the pH of the developer ended up lowering the film speed by an unexpectedly large amount. (However, I did not make the comparison to Fomapan 400 in other developers, so my conclusions are tentative.)

By the way, when I did a similar test with Fomapan 100 (using the HC110 witch's brew mentioned above) I was getting about 1 stop below box speed (or maybe 2/3 stop below box speed), so perhaps the witch's brew developer is particularly ill-suited to Fomapan 400, at least as far as film speed is concerned.

 

[Photo Engineer]

With matched contrast??

 

[alanrockwood]

With matched contrast??

Yes.

Here's a graph of the results. The upper line is comparable contrast to the Fomapan 100 test results.

Note: The speed point for the two development times was virtually the same, so I am only showing one on this figure.

 

[Photo Engineer]

Is that 0.50 vs 0.61?? That is quite a mismatch if I read it right.

PE

 

[alanrockwood]

Is that 0.50 vs 0.61?? That is quite a mismatch if I read it right.

PE

Yes, the two curves had different Gbar, 0.61 for the upper curve and 0.50 for the lower curve. The best development time could be could be half way between (6 minutes 45 seconds) which would give a gbar of about 0.55.

By the way, the contrast for the upper curve (0.61) is pretty close to the way iso defines their test procedure, which (as you know) is based on the slope between the speed point and a point on the curve that is 1.3 log_base_10 exposure units more exposure.

By the way, I am not sure what is the "official" difference between the speed point and the zone V metering point. I have recently been assuming that 3.3 log_base_10 exposure units is about right. I believe the zone system aficionados like to use 4 log exposure units, but in regard to this I have heard that the zone system folks like to use denser negatives than many other people do

 

[Ian Grant]

I wonder if Agfa purposely formulated APX100 to perform well in Rodinal, given the fact that Rodinal was one of their important products.

I missed this bit yesterday Well APX100 and APX25 were the upgraded versions of AP100 and AP25 both of which were superb films, I guess every manufacturer rests their new film emulsions in their own main selling developers. I didn't notice any particular improvements but I was predominantly shooting 5x4, and the AP25/APX25 in a roll film back, I think it was a bit like the differences between FP4 or HP5 and FP4 Plus and HP5 Plus, in terms of film speed and developing times there was no changes needed.

We assume that a developer like D76/ID-11 is ideal for all films, but Kodak realised that the developer didn't bring out the best in the case of Tmax films, so released Tmax developer and then Xtol, I'd agree with Kodak's own comparison chart which shows Xtol to be their best all round developer., I used it as well as Rodinal, and with TMax and APX films the results were indistinguishable.

Ian

 

[Bill Burk]

3 1/3 or 4 aren’t log_base_10 exposure units in that context. That’s a count of f/stops. An f/stop is 0.3 log_base_10, each third-stop is 0.1 log_base _10 so the speed point to metered gray is 1.0 log_base_10 in standard model and in Zone System it’s four stops which is 1.2 log_base_10

The 0.2 difference is an interesting difference between the two methods.

 

[alanrockwood]

3 1/3 or 4 aren’t log_base_10 exposure units in that context. That’s a count of f/stops. An f/stop is 0.3 log_base_10, each third-stop is 0.1 log_base _10 so the speed point to metered gray is 1.0 log_base_10 in standard model and in Zone System it’s four stops which is 1.2 log_base_10

The 0.2 difference is an interesting difference between the two methods.

You are right. As you correctly say, 3.3 f/stops is about 1 log base 10 unit. I may be communicated poorly on this. My graph refers to 3.3 stops difference (which is correctly described), but my later post incorrectly identified this difference as 3.3 log base 10 units, which is incorrect. Thanks for catching this.

 

[RalphLambrecht]

Some people won't believe just how fine the grain can be with some films and Rodinal, but then it was Agfa's recommended developer for AP100 and later APX100. I remember the first film I shot with my Leica M3 & 50 Summicron it was Agfa AP100 developed in Rodinal and the quality was stunning.

Ian

Yes, I had the same experience. I started to wonder:why use anything else? But, I came back to D76 1+1 for a great compromise between speed,grain and tonality for almost any film.