Rotation development and time compensation for repeated use

[ghwilliam1903]

Hi everyone,

I recently purchased a rotary development tank and am planning to process C-41 film at home. The tank I acquired is a Jobo 1530 (a 1520 base tank + a 1510 extension). For chemistry, I’m using Cinestill C-41 in powder form, mixed to make 1 liter of solution.

According to the tank specifications, 240 ml of chemistry is required for rotary development of two rolls of film. To simplify measurement, I plan to use 250 ml.

Cinestill’s manual states that 250 ml is sufficient for two rolls of 36-exposure film, so for my first development, I intend to use a processing time of 3m30s.

However, I’m unsure about the development time when reusing the same chemistry for a third and fourth roll. Many online sources suggest increasing the time by 4% (*1.02 per roll), which would result in 3m38s. However, I assume this recommendation applies when replenishing used chemistry with fresh chemistry.

Another possible approach is using 4m04s—this is based on the fact that 1 liter of chemistry is designed for eight rolls of 36-exposure film. By this logic, developing two rolls in 250 ml is equivalent to developing eight rolls in 1 liter, which suggests following the development time for the final stages of the solution’s lifespan.

Does anyone have experience developing C-41 film with rotary processing? I’d appreciate any insights or recommendations on adjusting development times for reused chemistry.

Thank you, and happy developing!

 

[koraks]

Cinestill’s manual states that 250 ml is sufficient for two rolls of 36-exposure film

So logically, there should be no second time using this developer if you're going to use 250ml for 2 rolls, which indeed seems like a plausible capacity.

I intend to use a processing time of 3m30s.

Yes, oddly, Cinestill Cs41 is pretty much the only quasi-C41 developer that does not adhere to the industry standard of 3m15s. I've always found this puzzling.

However, I assume this recommendation applies when replenishing used chemistry with fresh chemistry.

No, a replenishment system is characterized by replenishment with a replenisher, and this is intended to keep other processing factors stable. If people use lengthening factors for development time, this usually indicates they're reusing the same developer without change. This induces inherent process drifts which at some point become noticeable and bothersome. Where that point is, depends on how strict your standards are, what your expectations are from the negatives, what you do with the negatives and how closely you're paying attention to the results. This explains why some people are perfectly OK with reusing developer far beyond the point where others wouldn't touch it anymore.

Does anyone have experience developing C-41 film with rotary processing?

Plenty. Most of the time I do a single roll of 35mm in a Jobo 1510 with 150ml of developer, which I use one shot. For 120 and/or two rolls of 135 in a 1520 tank, I use 250ml. For 2 rolls of 135 I also use the 250ml volume one shot. If I process a single 120 roll n 250ml, I may sometimes save the developer and then use it for a subsequent development session that I find non-critical (which, granted, is most of what I do). But I have to point out that I use minilab chemistry which I buy in larger quantities than a typical home-use kit (e.g. 12.5L of developer), which I store in such a way that it keeps in like-new condition for well over a year. The costs per roll are in this way low enough to not bother with re-using the developer.

I can't give any concrete suggestions for extending development time when reusing C41 chemistry. To the best of my knowledge, no concrete data has ever been published (at least online) that makes clear what the effects of repeated reuse of C41 developer are. We do know/can reasonably expect that several effects play a role, such as pH shift, developer depletion through oxidation and buildup of halides in the developer that leach out of the film. What those effects are and how strong they are depend on the kind of film processed, the way the developer is used and stored, and the period over which the developer is kept around. It will also depend on the chemical makeup of the developer. Thus, there are many, many variables and most of these are unknown. The only thing we know for sure that there will be an effect on negative quality; we just don't know how big that effect is, let alone if it's something that you in particular want to worry about (or rather - at what point you start worrying about it).

Having said all that, extensions in the order of 5% sound plausible to me. Whatever you do, I'd limit the reuse and not be tempted to keep going because "the scans still look fine to my eye." You may regret this later on as you learn more about scanning, perhaps start wet printing your negatives and figure out that the negatives you thought were fine, end up not being so good after all. For your specific situation, I'd be inclined to suggest reusing the 250ml volume only once, and not more than this. I also suspect that when doing so, a minor extension of the development time will end up having an insignificant effect over just using the regular process time, so I wonder how much thought should be put into this in the first place.

 

[pentaxuser]

Cinestill’s manual states that 250 ml is sufficient for two rolls of 36-exposure film, so for my first development, I intend to use a processing time of 3m30s.

I can't give an answer as I have never used Cinestill but if it is saying that the 250ml is needed for 2 films then doesn't that suggest that the safest method is to develop 2 fílms in 250ml then dump the developer and use fresh developer from the 1L for the next two films etc

Then, as you are using fresh developer each time you can stick with the same required Cinestill time on every occasion?

My post was obviously being written while koraks was posting but he seems to be saying the same thing as I have

pentaxuser

 

[Samu]

Yes, oddly, Cinestill Cs41 is pretty much the only quasi-C41 developer that does not adhere to the industry standard of 3m15s. I've always found this puzzling.

I don´t touch CineStill C-41 developer even with a long stick, but I have found this interesting. It has a non standard developing time in a non-standard temperature (39°C). I have wondered is there really a difference in the chemistry, or are they trying to compensate for developing in a tank without submerging it in the bath, i.e. letting it cool on the table for three and halve minutes. Every variant used in industry has the developer time and temperature standard, even if bleaching and fixing do differ in C41RA and its variants from the original Kodak version.

 

[koraks]

Yes, that's an interesting point, concerning the compensation for a cool-ish tank.
The really odd thing of course is that for all I known, the Cs41 stuff is actually manufactured in Rochester, NY - that's right, at the Kodak park. So for all my cynicism/skepticism, it does appear that the people who make it should be expected to know how it's supposed to work.

 

[Samu]

I can't give any concrete suggestions for extending development time when reusing C41 chemistry. To the best of my knowledge, no concrete data has ever been published (at least online) that makes clear what the effects of repeated reuse of C41 developer are. We do know/can reasonably expect that several effects play a role, such as pH shift, developer depletion through oxidation and buildup of halides in the developer that leach out of the film. What those effects are and how strong they are depend on the kind of film processed, the way the developer is used and stored, and the period over which the developer is kept around. It will also depend on the chemical makeup of the developer. Thus, there are many, many variables and most of these are unknown. The only thing we know for sure that there will be an effect on negative quality; we just don't know how big that effect is, let alone if it's something that you in particular want to worry about (or rather - at what point you start worrying about it).

There is one source I know - the instruction sheet which comes with the Fuji Hunt Film X-press 5 liter kit. This is a standard C.41 chemistry. It says of course, that for perfect results, one shot developing should be used.