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  1. #1
    markkubis's Avatar
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    C41 quality at slightly lower temperature

    The standard C41 development time is 3:15 at 100F (38C)

    However, I develop using a 4 reel hand inversion tank and it takes about 25 seconds to fill or to empty. I am looking to lower the temperature to extend the development time to about 5 minutes to reduce error and inconsistency.

    Rayco's book in the UK gives a C41 recipe and suggests that 95F (35C) at 5 minutes is an alternative to the official time.

    Would I be at risk of compromising quality in any way by going at this lower temperature (and also extending subsequent baths at the lower temperature) even if I were to use a branded C41 kit? Has anybody any experience of this?
    Last edited by markkubis; 07-04-2007 at 09:36 AM. Click to view previous post history. Reason: additional info

  2. #2
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    Yes, you would compromise quality.

    Color processing in C41 is a diffusion limited process that was designed around a temperature of 100 F. If you change it, the yellow layer tends to overdevelop and/or the cyan layer tends to underdevelop. This causes crossover.

    PE

  3. #3

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    http://www.kodak.com/global/plugins/...ls/z131_03.pdf

    Page 7
    In some rotary-tube
    processors, maintaining the developer temperature at
    37.8 ± 0.15°C (100 ±0.25°F) can be difficult, and often
    some loss of developer temperature occurs. The amount of
    developer-temperature loss can vary based on the design of
    the rotary-tube processor and the ambient conditions. Since
    the developer is the most critical step in the process,
    compensating for developer-temperature loss will help to
    optimize the performance of the process and improve the
    quality of the processed film.
    The best way to compensate for loss of developer
    temperature is by increasing the developer time (from the
    standard time of 3:15). The amount of developer-time
    extension can be determined approximately by the visual
    appearance of the density of processed film. The preferred
    method for determining the exact amount of developer-time
    extension required is to use KODAK Controls Strips.
    Process C-41 to monitor the process.
    So you can extend the time. Kodak even suggests it. The problem is figuring out how long at what temp.

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    I put quite a lot of effort into doing just this sort of thing. I wasted a LOT of 4x5 Portra VC trying to get a good image. As I said in my first post, the usual result was high yellow contrast and/or low cyan contrast.

    I think that the result Kodak was talking about might be limited to 1 deg C or so, but I personally would not do it.

    PE

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    If the problem is the long fill time, you can pre-fill the tank and put the reels in, in the dark. Truly a PITA, but it would address your problem of getting the full time for all the film at the recommended temperature.

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    It is not difficult to pre-fill a tank with C-41 developer then drop the film in, put on the lid and turn on the lights. It is only the developer that has critical time/temperature constraints. I have done this for years. When doing small tank processing of C-41, I use a deep print tray as a water bath for the chemicals and for the tank to sit in. I have temperature regulated water flowing into the tray constantly. The developer in the tank stays on-temperature since the tank is sitting in the temperature controlled water bath. This is really quite easy.

  7. #7
    AgX
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    C-41 at 30°C

    I find the experiences PE made over the years very interesting.
    Especially as here in the past special low temperature kits had been on the market.

    Tetenal, a renown German manufacturer for the professional as well as the amateur world still recommends 30°C as an alternative to the common 38°C for their `Colortec´ range. This includes 2-bath non-regenerating processes as well as 3-baths regenerating processes intended for roller-transport machines. And this is done not somewhere as a marginal note, but next to their 38° times. I phoned them and was reassured about that. However they do not recommend pushing employing their kits, with the exception of multispeed films (which no longer are offered).

    I also asked Amaloco, a Dutch manufacturer, and was told that the C-41 films had changed over the last years what made a 30°C processing no longer feasible.

    That all is quite puzzling…

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    I exaggerated by a bit, a lot of how easy it is, or not, depends on your darkroom layout. For me, my wet area is pretty cramped, 4 rolls would take a bit of choreography. No, it's not difficult.

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    By accident I have developed some C-41 films at lower temperature (it was around 34-35°C) and the color cast of the shots is almost impossible to treat after scanning - and I adjusted the time, but only to slightly more around 4mins.

    When developing sheet film in the HP CombiPlan tank, I have also resorted to prefilling the tank in the dark, as it takes some 30seconds to fill the tank with the lid closed.

    I am even able to pour out the developer out of the tank, in the dark grope for the blix, pour in the blix, close the lid and start some agitation.

    As for the drop in temperature, it's important to preheat the tank itself (let it lie open and submerged in the tempering bath for at least 5 minutes). Also I keep the tempering bath at 40°C, when I pour the developer in and start the agitation, the temperature is around 39°C, after the 3:15 development, the temperature is not much lower than 37.5°C...
    Jiri Vasina
    www.vasina.net

  10. #10
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    Quote Originally Posted by AgX View Post
    I find the experiences PE made over the years very interesting.
    Especially as here in the past special low temperature kits had been on the market.

    Tetenal, a renown German manufacturer for the professional as well as the amateur world still recommends 30°C as an alternative to the common 38°C for their `Colortec´ range. This includes 2-bath non-regenerating processes as well as 3-baths regenerating processes intended for roller-transport machines. And this is done not somewhere as a marginal note, but next to their 38° times. I phoned them and was reassured about that. However they do not recommend pushing employing their kits, with the exception of multispeed films (which no longer are offered).

    I also asked Amaloco, a Dutch manufacturer, and was told that the C-41 films had changed over the last years what made a 30°C processing no longer feasible.

    That all is quite puzzling…
    I think you have the key to it right here!

    The films have changed quite a bit over the years, and they all differ. The one thing in common is that they all reach the same optimum at 100 F, not anywhere else.

    This is the reason that so many people have problems with the old Dignan 2 part C41 developer. Films vary in thickness, therefore in diffusion rate of developer, and therefore have different sensitivities to temperature.

    We drew time/temperature charts to insure that all curves of all emulsions reached the exact optimum point at 3.25' at 100 F. Anything else may not meet that release criterion.

    PE

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