JOBO TIMES

Discussion in 'B&W: Film, Paper, Chemistry' started by Bruce Osgood, Nov 18, 2011.

  1. Bruce Osgood

    Bruce Osgood Membership Council Council

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    Below is a cut and paste from Jobo instruction sheets discussing development times:

    JOBO: If you do not want to use a pre-rinse, you will need to determine the appropriate developer time for each specific situation. Rotary agitation affects different film and developer/dilution combinations to differing extents. Some developing times may be essentially the same, while others are significantly shortened or even extended. As a rough guide, try shortening the developer time by about 15%. This could vary by anywhere from about -25% to +10% from the original 'hand process' (intermittent agitation) times. A five minute 'pre-warm' is recommended when foregoing the pre-rinse. This time allows the film, reel(s), and tank to stabilize at the development temperature, before the developing begins.

    I read this as saying if you use a pre-rinse you do NOT shorten the development time from the 'hand process (intermittent agitation) time but you MAY find an adjustment necessary due to the film and developer in use. And if you do not use a pre-rinse you should expect to make an adjustment in time from -25% to +10%.

    This is contrary to my understanding of using a Jobo. I am under the impression that you ALWAYS shorten the development times by 15% (as a first step) whenever using the Jobo system with a pre-rinse.

    I never questioned this as I thought continuous rolling would produce results sooner than intermittent agitation.

    Do you read this as saying when using the Jobo system and pre-rinse, it is not mandatory to adjust time from suggested "hand process" times supplied from the film manufacturer?

    Thanks, in advance...
     
  2. Sirius Glass

    Sirius Glass Subscriber

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    Following Jobo's instructions, XTOL should not be used with pre-rinse and the time should be reduced 15%.

    Using the Jobo 3010 Expert Drum for 4"x5" sheet film, I found that XTOL replenished with Ilford HP5+ and no pre-rinse, required [the full development time of non-rotational processing plus one minute] adjusted for the temperature. Otherwise the film was under developed.

    Therefore:
    Does not apply with XTOL replenished, without pre-rinse. It appears that the 15% reduction is in part due to the pre-rinse rather than the rotary processing.

    Steve
     
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  3. pentaxuser

    pentaxuser Subscriber

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    That's exactly what John Tinsley found and reported on in his book on rotary processing in the 1990s. However his findings in the book were confined to 3 Ilford developers, namely ID11, Perceptol and Microphen and to 3 Ilford films, namely Pan F, FP4 Plus and Delta 400.

    I am intrigued as to what causes some combos of film and dev to require a longer time under rotation than inversion. You'd imagine that continual "washing" with dev could never give longer times. Somehow continual changing of the dev must slow the development of the film.

    pentaxuser
     
  4. Greg Davis

    Greg Davis Member

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    I use Xtol 1:1 single shot in a Jobo and find that I do not need to adjust the times at all. I used Kodak's J-109 sheet as a reference and they recommended the same time for both methods with my film. Testing on a densitometer and looking at the prints confirmed them for me. I should note that I do not use a pre-wet with either method.
     
  5. grahamp

    grahamp Subscriber

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    A pre-rinse will do several things. It will (if the water and the Jobo are at the right temperature) stabilize the film and tank temperature. It will remove the anti-halation dye in most cases. It may expand the gelatin of the film. It will saturate the gelatin with water. The last two probably cancel each other out. Certainly I have not found any need to change times with conventional (single solution, non-staining) developers when using a pre-rinse.

    I do not use a pre-rinse with split developers, such as Thornton's two bath. In this case I just have to be sure the tank is not exceptionally cold.

    I suspect the varying viewpoints are more to do with variations in manual processing than with the theoretical behavior of film during the first minute or so of wetting or development. Jobos are consistent, people as a group are not :cool:
     
  6. pentaxuser

    pentaxuser Subscriber

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    This may be the case but to back up one poster's findings the Kodak Xtol publication shows the rotary time for Plus X to be 15 secs longer than the inversion time. OK a little under 5% increase but an increase nonetheless. I am presuming that Kodak was consistent in its testing so I wonder what accounts for the increase?

    pentaxuser
     
  7. Bruce Osgood

    Bruce Osgood Membership Council Council

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    I wanted to thank you all for your responses. It never ceases to amaze me how dogmatic I (and many others) can be once we think we have learned something, ... like always reduce time by 15%.........

    I guess what has been reinforced is that there is never an always in photography. I guess I should not say never.
     
  8. grahamp

    grahamp Subscriber

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    With pre-rinse? I am not an Xtol user - strictly M-Q or just metol formula. The argument with rotary processing is that the constant motion reduces development times, while the reduced immersion/exchange of developer lengthens it. I would not argue that Kodak did not standardize on methods. I would argue that that methodology is poorly conveyed in the description of inversion agitation. Based on my own experience I think I tend to under agitate by inversion compared some, and there seems to be some correlation with tank capacity and occupancy.

    As long as the method works, I don't suppose the theory matters much.

    Maybe Xtol is absorbed more slowly as the thin film in a rotating tank than the saturation of immersion. Maybe it is not as 'wet'?

    Graham

     
  9. Sirius Glass

    Sirius Glass Subscriber

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    XTOL does not do well with pre-wetting. Kodak let Jobo know and Jobo replicated the issues. Jobo independently worked with XTOL and agreed with the recommendation. It is not a question of standardization, rather a trait of the product.