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  1. #1
    Swellastic's Avatar
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    Why is C-41 film so fast to develop?

    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. #2
    Rudeofus's Avatar
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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.
    Trying to be the best of whatever I am, even if what I am is no good.

  3. #3
    Thomas Bertilsson's Avatar
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    Quote Originally Posted by Rudeofus View Post
    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.
    Exactly. And, the developing time is just as long as it needs to be.
    For home users, there is instruction for how to develop the film at lower temperature, necessitating longer development time.
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  4. #4
    RPC
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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.
    Last edited by RPC; 02-18-2013 at 01:41 PM. Click to view previous post history.

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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. #6
    Rudeofus's Avatar
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    Quote Originally Posted by pentaxuser View Post
    Or is it the case that, commercial considerations aside, the likes of Kodak could have developed a satisfactory C41 process at 20C
    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.
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  7. #7
    Photo Engineer's Avatar
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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

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    Quote Originally Posted by Photo Engineer View Post
    Use a 100F prewet and then use a stop if needed.

    PE
    The stuff used for BW works for C41 too?

  9. #9
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    Yes.

  10. #10

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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.

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