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As per the official information from ILFORD (found here) the powder developers PERCEPTOL, ID-11 and MICROPHEN can be used as a stock solution or in dilutions of 1+1 and 1+3. I'm confused as to how many rolls can actually be developed with the dilutions, assuming those are used as one-shot developer.

According to the documentation PERCEPTOL can be used to develop 4 rolls of 135 (36 exposures) or 120 film per litre at stock strength. Used developer is to be poured back into the bottle to mix with the remaining developer. Suppose I use a Paterson tank where one 135 roll requires 300 ml of liquid and 2 rolls require 500 ml. I take it that would then let me do 4 developments of a single roll or 2 developments of 2 rolls at the same time, increasing development time after reuse as documented. Is this correct?

So let's say instead we use a dilution instead and only use the diluted developer once. At 1+1 I'd need 150 ml of stock to get 300 ml of developer. This would yield approximately 6 developments of 1 roll each at 300 ml (assume the remaining 100 ml stock isn't used). At 1+3 I'd need 75 ml of stock to get 300 ml of developer. This would yield approximately 13 developments of 1 roll each at 300 ml (assume the remaining 25 ml stock isn't used). Am I correct in this assessment or making some mistake in reasoning?

I find things get more confusing if 500 ml of developer would be made at 1+1 or 1+3 dilution, which in a Paterson tank suitable for 2 rolls could be used to develop 2 rolls simultaneously. At 1+1 you'd need 250 ml of stock to get 500 ml of developer. That should be enough for 4 developments, but with 2 rolls at the same time. Meaning 8 rolls total. At 1+3 you'd need 125 ml of stock to get 500 ml of developer. Enough for 8 developments, for 16 rolls total. Am I making a mistake in assuming 500 ml developer at 1+1 or 1+3 dilution can simply be used to develop 2 rolls simultaneously? Should the development time be increased in this case, as with reusing stock strength after each roll?

EDIT: as an added thought, for ID-11 or MICROPHEN this could put 1+1 dilution even at a disadvantage. Those developers can be used for 10 films per litre at stock strength. But if diluted they must be used one-shot. Then it would still only let you develop 6 single rolls at 1+1 (300 ml developer using 150 ml stock per roll) and 8 rolls in pairs at 1+1 (500 ml developer using 250 ml stock per 2 rolls).

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Your numbers sound correct.

When using multiple rolls of film in a given development run, you Do Not increase development times beyond what you would expect to use if doing a single roll.

If the chemistry calls for X minutes, then you should develop it for X minutes whether you have a 1 reel tank with 1 roll of film, or a massive 10 reel tank loaded with 10 rolls of film. - The chemistry used to cover the rolls contains the volume of chemicals needed to develop that roll [for the specified length of time], and the fact that there are other rolls in the same tank does not impact the required time.

Your time adjustments only need to take place if reusing chemistry to account for what has already been depleted a bit from a previous development.

An important thing to remember with the diluted one-shot development options is that they're great for consistency/reliability, and ease of use. There is no extra steps to track, no adjusting times based on past usage, etc. Mix your chemistry, pour in tank, develop as needed for film and exposure combination.

  • Using one-shot 1:1, you trade a few rolls in capacity for the roll to roll consistency.
  • Using 1:3, you gain a few rolls, but also increase your needed development times.

There will also be subtle differences in how your shadows and highlights appear between the different dilutions.

I personally prefer to just run with 1:1 ID-11 [or Kodak's D76 - They only differ in how they're mixed for shipping.] for simplicity.


And a fun side note: If you ever switch to working with medium format, Paterson tanks were actually designed for the longer 220 film - If you're brave you can actually load two 120 rolls onto a single reel by taping them together. There is however a risk of the rolls overlapping, and causing bad development, so this is something to be used with great care.

  • Interesting. I've read at some places that for PERCEPTOL a minimum of 70 ml or so of stock solution is necessary for the development of 1 roll. This due to how much surface area a given amount of developer can process. At 1+1 that's no issue, and at 1+3 when using 300 ml it's still 75 ml stock solution in there. 2 rolls in 500 ml however would work at 1+1 (250 ml developer = 125 ml per roll) but might risk depletion if used at 1+3 (125 ml developer = only 62.5 ml per roll). Could there be truth to that? – G_H May 21 at 16:28
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    Truth, edging to half-truth: The 70ml minimum is your safety bar level for the extreme end of things, as different exposure levels in a given area of film will exhaust your chemistry at different rates. As you dip below that 70ml level you'll be more likely to hit localized exhaustion and cause more noticeable under development. - This may or may not be a desired outcome, and is something worth experimenting with to see how you feel about the actual results. Photography is a blend of art and science, be wary of getting trapped by one or the other in your thinking. – TheLuckless May 21 at 17:00
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Developers are mixed with water to make up a stock solution according to directions on the package.

You must mix-up a whole package at a time due to the composition of the powdered ingredients. They are formulated and mixed in proportion but settling of the different densities of the powdered ingredients makes it impossible to mix a portion of the developer.

After the stock developer solution has been carefully mixed with minimal agitation to avoid mixing air, Now, the decision is how to mix and use developer in a working strength to suit your desired creative outcome.

You can use developer once and discard it. Many use this technique to ensure consistency because the development times are the same. For economy, the developer is diluted and the development time is extended to compensate for the reduced chemical activity of the diluted solution. This is called one-shot development. The manufacturer suggests different possibilities for dilution and development time combinations. In this case, mix-up (dilute) enough stock solution to make enough working solution to fill your tank. If you need 500 ml total working solution and you decide to use 1:1 dilution, you would use 250 ml stock solution and 250 ml water - to fill the tank. After you develop the film, you discard the developer.

You can use and re-use the developer stock solution too –— up until the developer is depleted. Each time you use the solution, some of the activity of the solution is used. For that reason, you must gradually increase the development time for subsequent rolls of film. Some do this for different grain effects and slightly faster processing times. Care must be taken to ensure you get consistent results by logging each use and proper increased development times for progressive re-use.

In either case, mix up enough developer working solution to fill your developing tank or tray to process your film. Then, either return the spent developer to the stock or discard the diluted developer after use.

You must only keep track of the developer film processing capacity if you use the stock solution as your working solution and reuse it over-and-over increasing the development time to compensate for loss of strength/chemical activity with each roll of film.

Good luck.

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