Sheet film testing...development

Discussion in 'B&W: Film, Paper, Chemistry' started by Dave Swinnard, Mar 5, 2009.

  1. Dave Swinnard

    Dave Swinnard Subscriber

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    Before I embark on a round of film/developer testing, I thought I would ask the following questions:

    Has anybody noticed any significant development differences between processing a single sheet of exposed film in a Jobo Expert drum or other multi-sheet, rotary processing unit and processing a "full-load" of film?

    Assuming a suitable quantity of developer, will my tests done with a single sheet of film in the drum provide different (enough to notice) results than subsequent runs with 4 to 6 sheets in the drum? (-assuming the quantity of developer used in each case is the same; enough for the "full-drum" conditions, a 3006 drum in my case, about 500ml of Pyrocat HD normally.)

    Thanks, Dave
     
  2. MikeSeb

    MikeSeb Member

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    I have noticed no significant difference, even between different drum sizes either full or lightly loaded. At least my Jobo (ATL-1500) does a good enough job with temp regulation and agitation consistency so that there is remarkable consistency.

    I think the key is, as you said, making sure you have enough developing agent, regardless of working-strength dilution, for the film surface area you are processing. This means, for instance, that every 8x10 equivalent needs about 100mL of Xtol stock, or 200-250mL D76 stock, or ~6mL HC-110 syrup.

    8x10 equivalent being a roll of 135-36, 120, or 4-4x5.
     
  3. ic-racer

    ic-racer Member

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    I can't answer that because I have never done it. Why? Because when I tested a one-foot length of 35mm film, processed alone, it comes out with a significantly higher gamma than a whole rool. In fact, because of that, I do my tests by exposing the step wedge on a whole 35 exposure roll and taking pictures with the rest of the roll before processing. Even then, the gamma will be slightly less than when the roll is processed together with 8 other rolls in the 1500 tank.

    It is kind of a 'Catch 22' because you don't want to waste 9 other sheets in your expert drum when you are not sure of the development time. What I would do is to zero in on a development time using a single sheets at a time and then expect that 10 sheets together will give less gamma (0.05 or so) and fine tune things with 10 sheets in the drum.

    BTW when I first tested a T-max 4x5 in the drum with 9 other sheets the gamma was very similar to 35mm T-max in the 1500 tank, so I was never in the situation you are in now.
     
  4. edtbjon

    edtbjon Member

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    Yes, ic-racer has a point in what he's saying. This is more of an issue with one-shot developers and Jobo processors, because of the rather large ratio of air in the tank (compared to the amount of developer).
    In a 3006 drum there's is room for 2-3000 ml, out of which most is air when used for processing. Combined with the constant agitation, it's inevitable that quite a lot of oxidation will occur. The situation is the same with the smaller "reel based" Jobo-tanks, where the developer takes up about 1/3 or less of the tank volume. (This is the very reason why e.g. PMK doesn't work that good in a Jobo.) So, unless you use the same (i.e. maximum) volume of developer, oxidation will be an issue.
    The second part of the problem is that if you use the developer volume for six sheets and develop only one sheet, the developer will not exhaust in the same way it would with six sheets.

    But as ic-racer says, you will get close enough and can fine-tune once you have your own personal starting times. The important thing isn't to have a "perfect" negative, but quite a good one. There is quite a lot of latitude to be found in the printing process. (I'm not saying that "sloppiness" is OK, rather to not get stuck with testing to find the perfect dev.time and missing out on a lot of real world photography time.)

    //Björn
     
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