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

KPtheamateur · Apr 2, 2020

Hi,
I've got a lovely new roll of Foma 100 to develop and being stingy with chemicals I usually like to dilute my ID-11 to 1+3. However, I also exposed the Foma 100 at EI 400, just to make things more complicated.

So I wanted to ask if anyone had any good rules of thumb when it comes to extending developing times.

The box says Foma 100 should be dev'd at about 6:30 in ID-11 stock, so how would you good people approach this?

pentaxuser · Apr 2, 2020

Hopefully someone here has used that combo but as you may have discovered, as I just have,that there is no combo of these 3 aspects in the Massive Development Chart There is Foma 100 @400 but only at 1+1

Lack of info on the MDC suggests that very few photographers have tried it. I'd be inclined to go with 1+1 and the time on the MDC. There may be those who do have a formula for you that gets you to a time for your combo but I suspect there may be some risk. It depends on how important the negs are

pentaxuser

markbau · Apr 2, 2020

I would avoid dilutions of 1:3 like the plague. A 36 exposure roll of 35mm needs at least 250ml of stock with most developers (very active developers like Rodinal are a different story) Developers are actually quite cheap in the photography food chain. Trying to save money with them is a false economy. Why ruin expensive film because you wanted to save a few pennies on the developer?

ic-racer · Apr 2, 2020

I think the best way to extend development time is to lower the temperature. Diluting developers can create a myriad of unwanted effects if all you want is longer development time.

bernard_L · Apr 2, 2020

Generally, in developer datasheets the high dilutions are not recommended for pushing. Rather use undiluted dev. And, the hard truth is that your roll is underexposed, period. Look at the manufacturer's datasheet: https://www.digitaltruth.com/products/foma_tech/Fomapan_100.pdf, curves on the left (20°C). Generally, at a G-bar of 0.6 (somewhere between the frequently suggested 0.55 and the 0.62 of the Iso norm) you just reach iso 100. And extending the time as much as you care, you reach 125 (almost 160 with Microphen). How acceptable that is with meter set to 400 depends a lot on the subjects that were captured on your film.

KPtheamateur · Apr 2, 2020

Thanks for such a flurry of replies so quickly!

@pentaxuser I checked MDC first of all and that was what made me curious about the relationship between development, dilution and EI. Pity, as it would have been very handy if I'd just missed it. I think you're right, I'll use the 1+1 and see. The negs aren't at all important, just messing around and showing my daughter how to use a camera, so the pictures don't have to last the ages. (I don't want to be rude to Foma, but if they were important I probably wouldn't be using Fomapan. Sorry Foma!)

@markbau we'll have to agree to disagree on 1+3 I think - while I don't use it all the time, I've never had it be a problem for me. I agree that ID-11 is cheap, that's the main reason I buy it, but this is Fomapan 100 so it's hardly breaking the bank either, even on my very limited budget. I didn't really explain in the OP, but this is very much a fun, mess-around kind of occasion, and I found myself curious about the relationship between the different elements of time, EI and dilution.

@ic-racer Thanks for the suggestion, as I say I was just curious about whether there were rules of thumb that people have developed over the years, rather than extending developing time for it's own sake, but I will bear that in mind.

@bernard_L thanks for the link to the data sheet, that's very helpful. You have solved the immediate problem!

due to its wide exposure latitude the film gives good results even when overexposed by 1 EV (exposure value) (as ISO 50/18o) or underexposed by 2 EV (as ISO 400/27o) without any change in processing, i.e. without lengthening the development time or increasing the temperature of the developer used

Thanks all for chipping in and helping me out

pentaxuser · Apr 2, 2020

KPtheamateur said:
@markbau we'll have to agree to disagree on 1+3 I think - while I don't use it all the time, I've never had it be a problem for me. I agree that ID-11 is cheap, that's the main reason I buy it, but this is Fomapan 100 so it's hardly breaking the bank either, even on my very limited budget. I didn't really explain in the OP, but this is very much a fun, mess-around kind of occasion, and I found myself curious about the relationship between the different elements of time, EI and dilution.

@ic-racer .

@bernard_L thanks for the link to the data sheet, that's very helpful. You have solved the immediate problem!

due to its wide exposure latitude the film gives good results even when overexposed by 1 EV (exposure value) (as ISO 50/18o) or underexposed by 2 EV (as ISO 400/27o) without any change in processing, i.e. without lengthening the development time or increasing the temperature of the developer used

On 1+3 we are back to the old argument as to what is the minimum quantity of stock solution needed. I can see no reference to there being a minimum quantity of ID11 when developing a film on a one-off then dump basis and certainly when I wrote to Ilford about min quantity of Perceptol for a 135 film I was given a reply that suggested that it might be about 75ml of stock. In fact I got away with less than that as my Jobo 135 tank only holds 250ml so it was 62.5 ml

I should add that this was for HP5+ where Perceptol at 1+3 will manage a speed of 320. The problem at 1+3 even for ID11 would appear to be push processing as In your case but Foma's own specs would seem to support a two stop push without any change to time or temp.

This seems to be quite a bold statement but we need to ask why would Foma make this unless it had evidence of it being correct?

Les us know how the negs turn out

pentaxuser

David Allen · Apr 2, 2020

There is a long standing (at least from the 1930s if not before) 'rule of thumb' that will give you a starting point. This is that you multiply the recommended development time by 1.5 for each stop you have pushed.

So, if Foma recommend a normal development time of 6:30 you calculate the time for a two stop push as follows:

6:30 is 6.5 minutes.

6.5 x 1.5 = 9.75 = 9 minutes and 45 seconds = ISO 100 at EI 200

9.75 x 1.5 = 14.63 = 14 minutes and 38 seconds = ISO 100 at EI 400

I am sure that you are aware that you can't really 'push' film. What you are doing is deliberately underexposing the film to give you a shutter speed / aperture suitable for the environment where you want to make a photograph. The purpose of the extended development is to 'stretch' the limited amount of exposed silver to give you a good contrast range from the limited data that your film has recorded.

Bests,

David.

Please note that the temporary address for my website is: http://dsallen.carpentier-galerie.de

KPtheamateur · Apr 5, 2020

pentaxuser said:
On 1+3 we are back to the old argument as to what is the minimum quantity of stock solution needed. I can see no reference to there being a minimum quantity of ID11 when developing a film on a one-off then dump basis and certainly when I wrote to Ilford about min quantity of Perceptol for a 135 film I was given a reply that suggested that it might be about 75ml of stock. In fact I got away with less than that as my Jobo 135 tank only holds 250ml so it was 62.5 ml

I should add that this was for HP5+ where Perceptol at 1+3 will manage a speed of 320. The problem at 1+3 even for ID11 would appear to be push processing as In your case but Foma's own specs would seem to support a two stop push without any change to time or temp.

This seems to be quite a bold statement but we need to ask why would Foma make this unless it had evidence of it being correct?

Les us know how the negs turn out

pentaxuser

Just thought I'd check back in to say how the negs turned out in the end. They're currently hanging up in front of me to dry, and I have to say they're looking pretty good! Will be able to see better when I've done a contact sheet, but I'm seeing some pretty well exposed images, and I think the only obvious problems are where my daughter didn't take the lens cap off. So, seems like Foma weren't kidding about the processing.

I just used MDC's timing for 1+3 @ ISO 100 in ID-11 btw, no rules of thumb

KPtheamateur · Apr 5, 2020

David Allen said:
There is a long standing (at least from the 1930s if not before) 'rule of thumb' that will give you a starting point. This is that you multiply the recommended development time by 1.5 for each stop you have pushed.

So, if Foma recommend a normal development time of 6:30 you calculate the time for a two stop push as follows:

6:30 is 6.5 minutes.

6.5 x 1.5 = 9.75 = 9 minutes and 45 seconds = ISO 100 at EI 200

9.75 x 1.5 = 14.63 = 14 minutes and 38 seconds = ISO 100 at EI 400

I am sure that you are aware that you can't really 'push' film. What you are doing is deliberately underexposing the film to give you a shutter speed / aperture suitable for the environment where you want to make a photograph. The purpose of the extended development is to 'stretch' the limited amount of exposed silver to give you a good contrast range from the limited data that your film has recorded.

Bests,

David.

Please note that the temporary address for my website is: http://dsallen.carpentier-galerie.de

Thanks very much for the rule of thumb David, this is exactly the kind of thing I thought some of the members here might have knowledge of! I will definitely make use of it in future, for those times where MDC can't just tell me what to do ...

Vaughn · Apr 5, 2020

Sorry if you have seen this already...but it might be of help for part of your inquiry.

https://www.digitaltruth.com/devchart.php?doc=timetemp

bnxvs · Apr 6, 2020

David Allen said:
There is a long standing (at least from the 1930s if not before) 'rule of thumb' that will give you a starting point. This is that you multiply the recommended development time by 1.5 for each stop you have pushed.

More precisely, the square root of 2 (1.41) ...

Adrian Bacon · Apr 6, 2020

KPtheamateur said:
Hi,
I've got a lovely new roll of Foma 100 to develop and being stingy with chemicals I usually like to dilute my ID-11 to 1+3. However, I also exposed the Foma 100 at EI 400, just to make things more complicated.

So I wanted to ask if anyone had any good rules of thumb when it comes to extending developing times.

The box says Foma 100 should be dev'd at about 6:30 in ID-11 stock, so how would you good people approach this?

Well, ID-11/D-76 should use a minimum of 250-300ml of stock solution per 80 square inches regardless of dilution, so you really shouldn't be diluting it to try to stretch it further as that leads to really inconsistent development results from film to film, especially in the highlight portions of the image.

The point of diluting D-76 is to achieve a different look, not to save developer. Of course, people can and should do what they want, however, my advice is to start with either stock, or 1+1, do 300ml of stock regardless of how its diluted and go from there. If you like 1+1 (300ml stock + 300ml water) and want to try more dilute, get a larger tank and try it out, just keep in mind that you're looking at having at least a liter of total solution volume at 1+3 (300ml stock + 900ml water). I would be very cautious about using less than 300ml stock per roll of film as it really does lead to development that you can't consistently rely on. Many people will say that they don't see any difference when using less stock, however, I've actually measured it and the highlights really do build less density when you have less stock solution. That by itself isn't really a problem, the problem is how much highlight density variation that happens will vary depending on the content of the images. Images that are relatively low in contrast for most of the roll will see little to no variation, images that are mostly high contrast for most of the roll will see a lot of density variation, and images that are in-between will see some middle ground between the two. What happens to the highlight densities is very inconsistent when you don't have enough stock solution.

If you're OK with that, then by all means, go for it, but I'd rather have consistent development if it were me.

pentaxuser · Apr 6, 2020

Adrian Bacon said:
I would be very cautious about using less than 300ml stock per roll of film as it really does lead to development that you can't consistently rely on. Many people will say that they don't see any difference when using less stock, however, I've actually measured it and the highlights really do build less density when you have less stock solution. .

So just to be clear: If I use a Jobo or Durst tank which only hold 250mls then I will get development that I cannot consistently rely on? While your meaurements( densitometer?) reveal that highlights will "suffer" for want of a better word could you detect this by eye and then on a print?

Thanks

pentaxuser

Adrian Bacon · Apr 6, 2020

pentaxuser said:
So just to be clear: If I use a Jobo or Durst tank which only hold 250mls then I will get development that I cannot consistently rely on? While your meaurements( densitometer?) reveal that highlights will "suffer" for want of a better word could you detect this by eye and then on a print?

Thanks

pentaxuser

yes. D-76 is not well suited to processing with smaller tank sizes because of this. If you have a smaller tank size, you’re better off using either XTOL (100ml minimum), or HC110, or Rodinal, or similar where you can

it’s hard to see by eye alone because it doesn’t destroy the highlights, they just don’t have as much density.

I’ll see if I can dig up the data I did on this and post it here. This was 2-3 years ago when I did it.

pentaxuser · Apr 6, 2020

Adrian Bacon said:
yes. D-76 is not well suited to processing with smaller tank sizes because of this. If you have a smaller tank size, you’re better off using either XTOL (100ml minimum), or HC110, or Rodinal, or similar where you can

it’s hard to see by eye alone because it doesn’t destroy the highlights, they just don’t have as much density.

I’ll see if I can dig up the data I did on this and post it here. This was 2-3 years ago when I did it.

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

KPtheamateur · Apr 6, 2020

Adrian Bacon said:
yes. D-76 is not well suited to processing with smaller tank sizes because of this. If you have a smaller tank size, you’re better off using either XTOL (100ml minimum), or HC110, or Rodinal, or similar where you can

it’s hard to see by eye alone because it doesn’t destroy the highlights, they just don’t have as much density.

I’ll see if I can dig up the data I did on this and post it here. This was 2-3 years ago when I did it.

I recognise that there are lots and lots of people on here who will have decades of darkroom experience and I do appreciate the value of a consistent quality of negative to help with workflow.

On the other hand, I started this thread on the premise that there would be rough rules of thumb, and by its nature a rule of thumb is a 'good enough' solution that is particularly useful in unusual situations. In the situation that made me start the thread in the first place, for example, I'd been messing around shooting Fomapan 100 in a Holga to show my toddler the basics of how a camera works. In that situation a rule of thumb is definitely good enough, I think.

On your specific point, which I don't contest as such - I haven't got a densitometer and am unlikely to ever have one - the film stocks I most like to use are Delta 100 and HP5+, and Ilford recommend a 1+3 dilution of ID-11 for maximum sharpness and for economy, for both these emulsions and it's certainly what I've used when developing it. I haven't noticed any visible inconsistencies and on 135 a £5 litre of ID-11 can last around a dozen one-shot devs (soewhat less on 120 of course), which I regard as an affordable situation. I'm very happy with the prints I've made from all my rolls. So I do take your point, but I'm not sure my photographic output is at a stage where any differences matter very much. Maybe as I get more experience and what I produce evolves it will be more significant for me.

Adrian Bacon · Apr 6, 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

The D-76 tech sheet is a good place to start: https://imaging.kodakalaris.com/sites/uat/files/wysiwyg/pro/chemistry/j78.pdf

Page 2 under the “development times” heading. In this 2017 version, they don’t explicitly call out 250ml as the minimum, but do give guidance as to what to do if you use less than their recommended minimum, which works out to 236.5ml of stock per roll when diluting 1+1.

MattKing · Apr 6, 2020

KPtheamateur said:
On your specific point, which I don't contest as such - I haven't got a densitometer and am unlikely to ever have one - the film stocks I most like to use are Delta 100 and HP5+, and Ilford recommend a 1+3 dilution of ID-11 for maximum sharpness and for economy, for both these emulsions and it's certainly what I've used when developing it. I haven't noticed any visible inconsistencies and on 135 a £5 litre of ID-11 can last around a dozen one-shot devs (soewhat less on 120 of course), which I regard as an affordable situation. I'm very happy with the prints I've made from all my rolls. So I do take your point, but I'm not sure my photographic output is at a stage where any differences matter very much. Maybe as I get more experience and what I produce evolves it will be more significant for me.

The minimum quantity recommendations are always somewhat challenging to evaluate because, when they start coming into play, the associated problems vary significantly with one's photographic subject.
If one shoots a lot of photos like this on a roll, there is relatively little exposed silver halide on the negative to exhaust the developer, so the minimum quantity probably won't come into play:

If, however, one shoots a lot of photos like this on a roll, there is relatively a lot of exposed silver halide on the negative to exhaust the developer, so the minimum quantity probably is likely to come into play:

Adrian Bacon · Apr 6, 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

Looking at Ilford’s tech sheet for ID-11: https://www.ilfordphoto.com/amfile/file/download/file/1829/product/708/

on the bottom of page 7 going into page 8, they state that each roll of film consumes 250-300ml of developer.

Adrian Bacon · Apr 6, 2020

MattKing said:
The minimum quantity recommendations are always somewhat challenging to evaluate because, when they start coming into play, the associated problems vary significantly with one's photographic subject.
If one shoots a lot of photos like this on a roll, there is relatively little exposed silver halide on the negative to exhaust the developer, so the minimum quantity probably won't come into play:
View attachment 243469

If, however, one shoots a lot of photos like this on a roll, there is relatively a lot of exposed silver halide on the negative to exhaust the developer, so the minimum quantity probably is likely to come into play:

View attachment 243470

+1

The parts of the negative that had more exposure consume more developer to build highlight density. How many frames you shot, the subject brightness range that you shot, how much overall exposure you gave each frame, and how long you develop it for all come into play into how much developing agent you actually need. The minimum just covers what would be consumed for most subject brightness ranges with normal exposure and normal contrast. I’m sure if you routinely shot HP5 at EI 50 in high contrast scenes, 250-300ml of ID-11/D-76 probably wouldn’t be enough developer.

pentaxuser · Apr 6, 2020

Adrian it might just be me but on both specs to which you have added links I cannot see where in the case of Kodak it quotes 236.5 ml as the minimum stock nor in the Ilford case in pages 7 going onto 8 it states each roll of film consumes 250-300ml of developer I have tried to copy and paste each section of which you mention into my reply so we can be sure that I am looking at what you are referring to so we know we are referring to the same sections but cannot

How do I do this or more simply can you copy and paste the Kodak and Ilford sections so we have the sections in front of us?

Thanks

pentaxuser

Adrian Bacon · Apr 6, 2020

pentaxuser said:
Adrian it might just be me but on both specs to which you have added links I cannot see where in the case of Kodak it quotes 236.5 ml as the minimum stock nor in the Ilford case in pages 7 going onto 8 it states each roll of film consumes 250-300ml of developer I have tried to copy and paste each section of which you mention into my reply so we can be sure that I am looking at what you are referring to so we know we are referring to the same sections but cannot

How do I do this or more simply can you copy and paste the Kodak and Ilford sections so we have the sections in front of us?

Thanks

pentaxuser

D-76 tech sheet:

“You can develop one 135-3 roll (80 square inches) in 473 mL (16 ounces) or two rolls together in 946 mL (one quart) of diluted developer. If you process one 135-36 roll in a 237 mL (8-ounce) tank or two
135-36 rolls in a 473 mL (16-ounce) tank, increase the development time by 10 percent (see the following tables)”

473ml of diluted developer (at 1+1) is 236.5ml of stock solution and 236.5 ml of water. This is for 1 roll of 135-36. Two rolls is double that, or 946 ml of total solution.

if you process one roll in 237ml of diluted developer (118.5ml stock + 118.5ml water) you need to increase the development time by 10% because the highlights don’t get as dense.

for Ilford ID-11:

“If a series of individual films is being developed in a spiral tank using 1 litre of stock ID-11 or MICROPHEN or PERCEPTOL, compensate for the loss of developer activity after developing the first film by increasing the development time 10% for each successive film, (see table below). This method of time adjustment relies on the used developer, (250 -300ml for one film), being poured back into the stock bottle and mixed with the fresh unused part of the developer before processing the next film. When using spiral tanks this helps to give more consistent results by reducing the risks of problems due to solution losses and the restraining effect of the by-products.”

it’s possible I mis-read the Ilford tech sheet and they mean that you need 250-300ml to cover the film.

pentaxuser · Apr 6, 2020

Thanks for taking the trouble to quote the relevant section of both companies data sheets and yes these were the sections to which I had thought you referred

In respect of the Kodak info sheet I now understand where you got your 236.5 ml of stock solution and I agree that it would seem to suggest that 236ml or very close to 250ml stock solution is required to develop one film if doing a 1+1 dilution. However it does go onto say that a 10% increase if developing one film of 135 film in a 273 ml tank is the alternative method so in that case it is surely 273 ml of 1+1 so in fact is 136.5ml of stock that is sufficient albeit at a 10% increase in time. So I feel it isn't as simple as saying that 250 or 236.5ml is the absolute irreducible minimum amount of stock

When replying about minimum quantities it was in the context of the OP's developer which was Ilford's ID11 when I asserted that I could not find any reference to a minimum stock quantity.

I agree that Ilford is referring to a replenishment regime in its info sheets and it kind of leaves the minimum stock quantity in a use once and dump process unsaid

So its reply to me about 75mls of stock Perceptol may be entirely consistent with the above.

So my conclusion is that Kodak's instructions in respect of D76 may well be clearer than Ilford's but certainly in respect of Perceptol as opposed to ID11 it made it clear that 75ml was sufficient for a 135 film in a what would have to be 300ml tank for 1+3

However while its answer y to me was solely pertaining to Perceptol as that is what I had inquired about, it certainly make no mention in its info of treating ID11 as a separate developer requiring different treatment

I will conclude that (1) in terms of minimum quantities it is open to interpretation and as they say: "You pays your money and takes your choice" and (2) there is sound evidence that as Matt said and you endorsed, it will depend on the nature of the scene in terms of how much is there to be developed

pentaxuser

Adrian Bacon · Apr 6, 2020

pentaxuser said:
Thanks for taking the trouble to quote the relevant section of both companies data sheets and yes these were the sections to which I had thought you referred

In respect of the Kodak info sheet I now understand where you got your 236.5 ml of stock solution and I agree that it would seem to suggest that 236ml or very close to 250ml stock solution is required to develop one film if doing a 1+1 dilution. However it does go onto say that a 10% increase if developing one film of 135 film in a 273 ml tank is the alternative method so in that case it is surely 273 ml of 1+1 so in fact is 136.5ml of stock that is sufficient albeit at a 10% increase in time. So I feel it isn't as simple as saying that 250 or 236.5ml is the absolute irreducible minimum amount of stock

When replying about minimum quantities it was in the context of the OP's developer which was Ilford's ID11 when I asserted that I could not find any reference to a minimum stock quantity.

I agree that Ilford is referring to a replenishment regime in its info sheets and it kind of leaves the minimum stock quantity in a use once and dump process unsaid

So its reply to me about 75mls of stock Perceptol may be entirely consistent with the above.

So my conclusion is that Kodak's instructions in respect of D76 may well be clearer than Ilford's but certainly in respect of Perceptol as opposed to ID11 it made it clear that 75ml was sufficient for a 135 film in a what would have to be 300ml tank for 1+3

However while its answer y to me was solely pertaining to Perceptol as that is what I had inquired about, it certainly make no mention in its info of treating ID11 as a separate developer requiring different treatment

I will conclude that (1) in terms of minimum quantities it is open to interpretation and as they say: "You pays your money and takes your choice" and (2) there is sound evidence that as Matt said and you endorsed, it will depend on the nature of the scene in terms of how much is there to be developed

pentaxuser

totally agree. People should do what works for them. If they’re not having any issues, then they’re not, and that’s fine. I personally think the added 10% time is very conservative. Kodak knows people are going to use less developer than what they probably should and the simple fact that you do need to add time is an acknowledgement that more developer would be better.

when I manage to rustle up the data for what I tested, I’ll post it here just for reference. I have it, I just need to find it and get it into a presentable form.

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

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