Why is C-41 film so fast to develop?

Discussion in 'Color: Film, Paper, and Chemistry' started by Swellastic, Feb 18, 2013.

  1. Swellastic

    Swellastic Member

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    Hello there. I recently made the jump into doing home processing of colour negative film. I found the whole process to be surprisingly easy and straightforward. However, the thing that struck me when i poured in the developer was how short the development time really is. If one were to try 3.15 minutes with any black and white film, it would probably lead to quite a bit of streaking and uneven development, wouldn't it? How is it that this doesn't happen with c-41 film? Pardon if I ask a question that has already been answered, but i got a bit curious after having carried out the process.
     
  2. Rudeofus

    Rudeofus Subscriber

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    First of all, quite a few people (including myself) have observed streaking with C41 when we didn't use a stop bath. Second, C41 was never intended for home use, but for big professional labs, where time on a machine equals money. Anything that could reduce processing time by a minute was worth a lot of money.
     
  3. Thomas Bertilsson

    Thomas Bertilsson Subscriber

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    Exactly. And, the developing time is just as long as it needs to be. :smile:
    For home users, there is instruction for how to develop the film at lower temperature, necessitating longer development time.
     
  4. RPC

    RPC Member

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    Developer diffusion into the emulsion layers occurs much faster at the 100 degree development temperature and chemical reactions in general take place much faster at higher temperatures.
     
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  5. pentaxuser

    pentaxuser Subscriber

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    Isn't this more than just a simple commercial trade-off in that, as I understand it C41 doesn't develop entirely satisfactorily at the kind of low temps that B&W is processed at. So am I right in saying that while C41 cannot have its developing temp lowered to room temp, neither can B&W have its temp increased to anything like 38C even such high temps were the commercially desirable ones at which to process?

    Or is it the case that, commercial considerations aside, the likes of Kodak could have developed a satisfactory C41 process at 20C and equally if the world was still B&W then then likes of Kodak etc could have and would have established a process suited to large scale labs at say 38C for a quick turn around and we amateurs would be struggling to find commercial chemicals that would process B&W at room temp because the "big commercial beasts" would have driven the amateur processor out of the market place?

    pentaxuser
     
  6. Rudeofus

    Rudeofus Subscriber

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    I guess they needed a certain (high) rate of diffusion to make all three layers develop in lockstep, and 38°C was the way to go. AFAIK some color negative process(es) before C41 could be run at room temperature, but for some reason C41 proved superior.
     
  7. Photo Engineer

    Photo Engineer Subscriber

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    CD4 is one of the most active color developing agents available. That is one key factor. The other is the relatively low contrast compared to reversal color films.

    DO NOT PROCESS C$Q FILMS AT ANY TEMPERATURE OTHER THAN 100 F. I have said this over and over. It is diffusion controlled and goes awry quite quickly with crossover, color shift sand etc.. if mishandled.

    Use a 100F prewet and then use a stop if needed.

    PE
     
  8. dwerg85

    dwerg85 Member

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    The stuff used for BW works for C41 too?
     
  9. Photo Engineer

    Photo Engineer Subscriber

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    Yes.
     
  10. tnabbott

    tnabbott Member

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    The 100F prewet and stop bath have worked very well for me. I never tried deviating from 100F because I am used to E6 developing. However, I only recently incorporated a stop bath in my process and it has made the results very consistent and predictable.
     
  11. Athiril

    Athiril Subscriber

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    B&W processing temps (20 celsius) of C-41 using the normal C-41 results in utter disappointment imho. dMax - dMin is terrible usually and is very difficult to separate tones, making high grain + noise whatever your process plus crap colour. If you want useable (other than 'lomo') results from room temp processing, alternative processing is required.

    30 celsius provides satisfactory results, in that you can get a colour image of good definition and fidelity (as opposed to 20c), but colour can be off by differing amounts from the highlight to shadow tonal scale instead of off by a consistent amount across that scale, and can be quite annoying to correct (highlights vs shadows may require different correction vs normal process which a single colour balance is excellent).

    I have not had a single problem with C-41 @ proper temp @ 3m 15s on any film using the following method (never had streaking, etc):

    Pre-Soak/Rinse (also gets tank+film up to temp) 40-42 celsius
    C-41
    Stop or Bleach or Blix
    Normal from here.

    Water stop/rinse after C-41 dev has caused problems for me after moving states and using a totally new water supply - in my case, high base fogging somehow. Until I started using stop or straight to bleach, then everything was dandy.
     
  12. pentaxuser

    pentaxuser Subscriber

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    Yes the point I was trying to discover and PE and others seem to have confirmed this is that the high temp of 38C and quick development isn't simply "time is money" driven. It is inherent in the process and likewise it would seem that in B&W there is a limit to what can be successfully done at very high temps.

    So the extrapolation of a line whereby dev time is shortened the higher the temp used, eventually breaks down no matter how much the "time is money" arch capitalists would prefer it not to :D

    pentaxuser
     
  13. Rudeofus

    Rudeofus Subscriber

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    Two things: before C41 was invented, other processes were used and these could be run at room temperature. So no, you don't have to run all possible color processes at 38°C, but C41 was evidently designed for operation at this temperature and will not work well above or below 38°C. It's all how you design the process. Note that such a process consists of emulsion and developer, so there's not much we can do about this.

    And second: b&w doesn't have the issue with color balance, so you could, in theory, run a b&w process way beyond 38°C. What will prevent you from actually doing this are the resulting extremely short dev times and in some cases considerable softening of the gelatin, but not the process itself.
     
  14. pentaxuser

    pentaxuser Subscriber

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    It sounds as if you are saying that it is "time is money" driven. The C41 process consists of the type of emulsion and developer that has been arrived at and we the users are not in a position to use the "wrong" temp with the existing process but in your opinion Kodak and others could have devised another process that would work at say room temp There is no inherent reason why it has to be 38C. It isn't governed by any absolute laws of chemistry or physics in the way that at sea level the boiling point of water can only be 100C

    Have I understood your reasoning correctly?

    As far B&W is concerned the limits are much greater than we currently use. We could go to 38C and at these temps the emulsion wouldn't be seriously compromised any more than it is in colour neg development? Presumably if 3 mins 15 secs doesn't create short development problems for colour then it wouldn't for B&W?

    pentaxuser.
    |
     
  15. Photo Engineer

    Photo Engineer Subscriber

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    Let me point out that C41 films contain DIR couplers. These are Development Inhibitor Releasers. They are designed to enhance color reproduction, sharpness and at the same time lower grain. The original process used was C-22 at 75 deg F. This worked to some extent in single layers, but did not in multilayers. Higher and higher temperatures were tried to no avail, and the image was just not right. Then two changes were made. They went from CD3 to CD4 and removed Benzyl Alcohol.

    Voila!

    The rest is history. The 9 or so emulsions in 14 layers were designed to work with the DIR couplers and this turned out to be 3' 15" at 100F. It was not 3' or 4', as this just did not work out right.

    At the same time, we were working with Ektaprint 3 and the new emulsions. We had to change the developer formula and then jack the temperature up to get 3' 30" for development time, even though our target was 3' at 85 deg F. The emulsions fought us every step of the way.

    You see, chemistry does not do what humans want. They behave according to strict laws and the result is C41 at 100F and don't mess around with it. I can attest to this as one who has studied the results and was working in the same office complex as the film and process was developed. I then went on to coat the film myself!

    If you process at any temp other than 100F, you stand a very good chance of getting quite substandard negatives.

    PE
     
  16. Rudeofus

    Rudeofus Subscriber

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    Like it or not, but you just confirmed my "time is money" theory. Even if it would have been possible to create a process that needed 10 minutes at 20°C, nobody would have wanted it back then.

    PS: I fully acknowledge that Kodak would not compromise on quality in order to reach that speed goal. After all they still use separate bleach and fix.
     
  17. Athiril

    Athiril Subscriber

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    There's a Fuji 2m 55s process time for one of their C-41 chemistry sets.
     
  18. Photo Engineer

    Photo Engineer Subscriber

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    Dan;

    Yes, and they probably spent $1M developing it and used every film possible to test it, unlike what most do. It is probably also patented. So, a simple change in time and temp to an existing developer might not work, but a total redesign might.

    Rudi;

    The process for paper at that time was using 6' development at 85F. We found that by removing Cadmium and Mercury, the emulsions in single layers developed in less than 3' at the same temp, so we aimed for 3' at 86 as all processes were using that in the '60s. We also had to change a lot of other things.

    PE