Rough Guide to relationship between dev times, ISO and dilution?

Adrian Bacon · Apr 12, 2020

Here's the data I did. Both rolls had the same exposure, both were developed in D-76 1+1 at the same temperature and same development time. The only difference between the two is 1 had 150ml stock solution for a total of 300ml, and one had 300ml stock solution for a total of 600ml.

Using less than 150ml will result in less density.

Also, as @MattKing said earlier, the density difference will vary based on how much the exposure varied for the subject being photographed when using smaller amounts of D-76. However, it can and does produce a measurable difference in the negative density when using less developer if everything else remains equal.

bernard_L · Apr 12, 2020

Adrian, loud applause to you for providing solid data. So many posts in other threads where hearsay replaces first-hand knowledge. Following what was mentioned earlier in this thread, it would be interesting to know if you processed a full roll in each case, and whether the other frames contained "average" subjects. Also, while the effect is very clearly there, it is (to me) quite instructive to see that there is (within the limits of the plot) no evidence of added compensation in the 150ml data: to zeroth order, the "150" film has less density, and to first order, less contrast (the two curves diverge slightly to the right), but no clear differential down curvature of the "150" curve wrt the "300" curve. This is fully consistent with the directions in Kodak publication J-78:

As already mentioned, there are several other factors presumably of similar importance: agitation schedule, calibration of one's thermometer, possibly alkalinity of tap water, intended development contrast according to scene contrast, etc... My take-home from your experiment is added confidence in Kodak's prescription of +10% when developing one 135 roll in 300ml of 1+1 D-76.

Adrian Bacon · Apr 12, 2020

bernard_L said:
Adrian, loud applause to you for providing solid data. So many posts in other threads where hearsay replaces first-hand knowledge. Following what was mentioned earlier in this thread, it would be interesting to know if you processed a full roll in each case, and whether the other frames contained "average" subjects. Also, while the effect is very clearly there, it is (to me) quite instructive to see that there is (within the limits of the plot) no evidence of added compensation in the 150ml data: to zeroth order, the "150" film has less density, and to first order, less contrast (the two curves diverge slightly to the right), but no clear differential down curvature of the "150" curve wrt the "300" curve. This is fully consistent with the directions in Kodak publication J-78:
View attachment 243750
As already mentioned, there are several other factors presumably of similar importance: agitation schedule, calibration of one's thermometer, possibly alkalinity of tap water, intended development contrast according to scene contrast, etc... My take-home from your experiment is added confidence in Kodak's prescription of +10% when developing one 135 roll in 300ml of 1+1 D-76.

both rolls where 24 exposures and had exactly the same images between them, so this is essentially best case. If you shot a full 36 and they were all high contrast, you’d see an even bigger difference.

pentaxuser · Apr 12, 2020

Thanks for the graphs, Adrian. There looks to be good evidence that 300ml of stock v 150ml does make a difference

On an all other things being equal what does this equate to in terms of a print from each neg. Where is the difference likely to show and is such a difference easily recognisable to the viewer of the two prints in terms of a clear improvement.

Thanks

pentaxuser

bernard_L · Apr 12, 2020

pentaxuser said:
Where is the difference likely to show and is such a difference easily recognisable to the viewer of the two prints in terms of a clear improvement.

Maybe I can propose some answer. The contrast (slope) between the "0" and the "4" points is 0.7058 for the red curve (300ml stock) and 0.6783 for the blue curve (150ml stock); and yes these are higher than the usual C.I. or G-bar values, because they are for the local gamma, perfectly normal. The ratio of these two gamma values is 0.9610, a 4% difference. Assuming the "red curve" negative would give an ideal print on grade 2 (ISO R-value 100), the "blue curve" negative would require, to provide a print of the same contrast, an ISO R-value of 96 (0.96x100). Grade 3 is ISO R=80. In other words, the difference is about 1/4 paper grade (slightly less).

pentaxuser · Apr 12, 2020

bernard_L said:
Maybe I can propose some answer. The contrast (slope) between the "0" and the "4" points is 0.7058 for the red curve (300ml stock) and 0.6783 for the blue curve (150ml stock); and yes these are higher than the usual C.I. or G-bar values, because they are for the local gamma, perfectly normal. The ratio of these two gamma values is 0.9610, a 4% difference. Assuming the "red curve" negative would give an ideal print on grade 2 (ISO R-value 100), the "blue curve" negative would require, to provide a print of the same contrast, an ISO R-value of 96 (0.96x100). Grade 3 is ISO R=80. In other words, the difference is about 1/4 paper grade (slightly less).

Thanks, bernard, that's makes it clear for me. Before we got to this stage in the discussion it had struck me that at 300ml min stock level using D76 becomes a much more expensive developer over the long run and maybe puts the DDX price into some perspective. If 150ml of stock results in the difference of 1/4 of a paper grade and really nothing else changes then this seem to be quite a high price to pay to shave 1/4 of a grade off in terms of paper grade when it achieves no other "benefit/improvement" for want of another way to describe the difference

pentaxuser

MattKing · Apr 12, 2020

The challenge when doing this analysis is that Adrian's test involves 24 exposure rolls, not 36 exposure rolls, so developer exhaustion probably doesn't need to be factored in.
In addition, Adrian's test probably doesn't involve a high key subject or anything else that might increase the likelihood of developer exhaustion.

Adrian Bacon · Apr 12, 2020

bernard_L said:
Maybe I can propose some answer. The contrast (slope) between the "0" and the "4" points is 0.7058 for the red curve (300ml stock) and 0.6783 for the blue curve (150ml stock); and yes these are higher than the usual C.I. or G-bar values, because they are for the local gamma, perfectly normal. The ratio of these two gamma values is 0.9610, a 4% difference. Assuming the "red curve" negative would give an ideal print on grade 2 (ISO R-value 100), the "blue curve" negative would require, to provide a print of the same contrast, an ISO R-value of 96 (0.96x100). Grade 3 is ISO R=80. In other words, the difference is about 1/4 paper grade (slightly less).

that sounds about right, for this specific scenario.

The thing to keep in mind here is this was for one film stock, with only only 24 exposures, none of which were high contrast. I developed each roll for the same amount of time, used the same temperature, and did the same agitation, which was 30 seconds initial, then 4 inversions at the top of every minute. I got the development time from massive dev chart. If you’re using a 250ml tank with only 125ml of stock, and everything else is equal, you’ll see an even bigger difference.

now imagine you’ve chosen an emulsion that is going to be your go to emulsion for most of your shooting and you’re trying to nail down a standardization for your normal, and N+/N- times for making prints. Not using enough developer is going to result in a different amount of negative contrast for every roll you shoot because the content of the scene will effect that. You might as well not have a standard negative, and shoot it however you like and use the minimum amount of developer possible because you’re going to be spending a fair amount of time on each image working out a print time and print grade. If you enjoy spending time in the darkroom and don’t mind doing that, then great. You have nothing to worry about. However, if time is money, then the cost difference of 300ml of stock per roll is nothing compared to the time spent dealing with a non-standard negative.

Again, people should do what works for them, and their choice, whatever it is, is fine.

bernard_L · Apr 12, 2020

pentaxuser said:
at 300ml min stock level using D76 becomes a much more expensive developer over the long run

Well, yes... and no.

Either you are an occasional consumer of film, say half a dozen par year; then probably you'll mix D-76 1 litre each time, twice a year. Looking at prices at fotoimpex.de, 1 litre (powder) costs 6€; paid twice a year:1 litre will develop 3 films, assuming, worst-case you use full strength, one-shot. Not worth thinking too long.

Or you are a prolific shooter. then buy gallon-sized 3.78 litre for 8.75€. Will develop 12+ films. Extra cost per film 8.75/12=0.73€, a 12% extra cost... Hint: if you want to mix D-76 gallon size, get hold of wine pouches (wine-in-bag). For some of them, the spigot can be dis-assembled, and the container cleaned and repurposed. The walls are engineered to be gas-tight, esp. to Oxygen. My experience is you can use the gallon over at least one year without any degradation.

Adrian Bacon · Apr 12, 2020

bernard_L said:
Well, yes... and no.

Either you are an occasional consumer of film, say half a dozen par year; then probably you'll mix D-76 1 litre each time, twice a year. Looking at prices at fotoimpex.de, 1 litre (powder) costs 6€; paid twice a year:1 litre will develop 3 films, assuming, worst-case you use full strength, one-shot. Not worth thinking too long.

Or you are a prolific shooter. then buy gallon-sized 3.78 litre for 8.75€. Will develop 12+ films. Extra cost per film 8.75/12=0.73€, a 12% extra cost... Hint: if you want to mix D-76 gallon size, get hold of wine pouches (wine-in-bag). For some of them, the spigot can be dis-assembled, and the container cleaned and repurposed. The walls are engineered to be gas-tight, esp. to Oxygen. My experience is you can use the gallon over at least one year without any degradation.

I use the refillable wine bag in a box system in my lab. Astropaq makes them if memory serves. I mix up 4 gallons at a time and that goes into a 16 liter bag/box.

I designed this particular test to see if a scenario that was least likely to induce a change in density actually did. Turns out, yep, it does, which for me in my lab means use a full 300ml per roll. Developer is cheap compared to the cost of time.

pentaxuser · Apr 12, 2020

Adrian Bacon said:
Turns out, yep, it does, which for me in my lab means use a full 300ml per roll. Developer is cheap compared to the cost of time.

If you have a lab and time is money I have no doubt you may be correct as indeed are the others who have since replied but I'd contend that most of us are not professional/commercial or have labs and for the home user who may be such a hobbyist for 20-30 or more years years then that person has to weigh the benefits from your top graph compared to the outcome from your bottom graph and weight that up against the extra cost over many years

pentaxuser

bluechromis · Apr 12, 2020

pentaxuser said:
Thanks the data would be useful. By the way is there an actual reference to 250ml or 300ml minimum stock quantity in either the Ilford or Kodak instructions and if so where is this to be found?

What has always made me question the minimum quantity of 250ml/300ml of D76/ID11 or Perceptol is why would a reputable company such as Ilford give a 1+3 ratio for Perceptol and not say in its instructions that in the case of 1+3 dilutions this means using a tank that holds 1 litre of fluid and that anything smaller carries risks of poor highlight densities and in the case of 135 film which is usually developed in 250 mls tanks the risks are so serious as to be almost inevitable. Indeed in the case of Perceptol I wrote to Ilford and received the reply that 75ml would be what it would regard as safe for satisfactorily developed negs. If Ilford has clearly established that 250ml is the minimum then I would have expected it to have warned me that anything less might work but using one quarter ( i.e. the 75ml it quoted) of its stated minimum stock quantity was inviting unsatisfactorily developed negs

The OP has reported that his negs at 1+3 as looking OK and if 250ml is the minimum then even if the film is 120 the best he will get into a Paterson tank is 150ml which is still a long way short of the 250ml/300ml that you say is needed. At 100/150ml short of the minimum stock that is said to be required by Ilford or Kodak I'd have expected the problem to which you refer to have shown up

So yes any reference to a stated 250ml/300ml minimum stock quantity would be useful

pentaxuser

Re: minimum amount of developer needed. Anchell and Troop say that although Kodak cited a smaller amount (150 ml x roll) of undiluted developer needed, that Kodak acknowledged that this was the bare minimum needed to achieve somewhat satisfactory results and much better results could be achieved using 250 ml of undiluted developer per roll (80 sq. inches). Anchell and Troop attributed the pretext for the lower number was for commercial labs using Versamat machine processors to achieve the greatest economy. (The Darkroom Cookroom 3rd Ed.)

bluechromis · Apr 12, 2020

Adrian Bacon said:
Here's the data I did. Both rolls had the same exposure, both were developed in D-76 1+1 at the same temperature and same development time. The only difference between the two is 1 had 150ml stock solution for a total of 300ml, and one had 300ml stock solution for a total of 600ml.

View attachment 243740

Using less than 150ml will result in less density.

Also, as @MattKing said earlier, the density difference will vary based on how much the exposure varied for the subject being photographed when using smaller amounts of D-76. However, it can and does produce a measurable difference in the negative density when using less developer if everything else remains equal.

Excellent work!

Adrian Bacon · Apr 12, 2020

pentaxuser said:
If you have a lab and time is money I have no doubt you may be correct as indeed are the others who have since replied but I'd contend that most of us are not professional/commercial or have labs and for the home user who may be such a hobbyist for 20-30 or more years years then that person has to weigh the benefits from your top graph compared to the outcome from your bottom graph and weight that up against the extra cost over many years

pentaxuser

absolutely. You should do what you want. You’re the only one who can decide if that works for you or not.

pentaxuser · Apr 12, 2020

Adrian Bacon said:
absolutely. You should do what you want. You’re the only one who can decide if that works for you or not.

Adrian, your qualified sentiments on this as above were made clear to me in our previous discussions and I thank you for that. The problem I find on Photrio is that when dealing with what are relativities we can so easily give the impression that we are dealing in absolutes from which no deviation can be countenanced without dire consequences.

This would have frightened me to death in my early days had I not had the benefits of being on a night school darkroom course where we used ID11 admittedly and not D76 but not at the minimum quantities then quoted for D76 The OP mentioned from the start that it was ID11 he was using

It may be of course that while both developers are said to be much the same, this may not be true in terms of minimum quantities or at least not the same as far as Ilford is concerned

pentaxuser

Adrian Bacon · Apr 12, 2020

pentaxuser said:
Adrian, your qualified sentiments on this as above were made clear to me in our previous discussions and I thank you for that. The problem I find on Photrio is that when dealing with what are relativities we can so easily give the impression that we are dealing in absolutes from which no deviation can be countenanced without dire consequences.

This would have frightened me to death in my early days had I not had the benefits of being on a night school darkroom course where we used ID11 admittedly and not D76 but not at the minimum quantities then quoted for D76 The OP mentioned from the start that it was ID11 he was using

It may be of course that while both developers are said to be much the same, this may not be true in terms of minimum quantities or at least not the same as far as Ilford is concerned

pentaxuser

yep. I’m fully aware that I’m talking to the internet (and all that that entails), and have no interest in picking a fight with anybody, so I generally try to couch things as suggestions or guidance based on my personal experience. Nobody is perfect, but if we all can be reasonably civil and willing to discuss, then that’s good enough for me.

From where I sit, there’s a pretty big difference between “you should” and “you have to” or “you must”. “You should” means things will be better if you do, but if you don’t, it probably won’t be the end of the world. “You have to” or “you must” means you’re swimming in shark infested waters if you don’t. Not good. Avoid if at all possible. That being said, most things in analog land (at least in my experience) fail softly, so even in “you must” situations it’s still fairly relative.

Rough Guide to relationship between dev times, ISO and dilution?

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