To clarify my question, I was thinking in terms of developing to the same density, not the same development time.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.
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.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?
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*16I 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
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.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.
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
I wonder if Agfa purposely formulated APX100 to perform well in Rodinal, given the fact that Rodinal was one of their important products.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
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.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?
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
Yes.With matched contrast??
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.Is that 0.50 vs 0.61?? That is quite a mismatch if I read it right.
PE
I wonder if Agfa purposely formulated APX100 to perform well in Rodinal, given the fact that Rodinal was one of their important products.
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.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.
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.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
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