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Thread: contrast control with rotary processing

  1. #1

    contrast control with rotary processing

    I use a JOBO rotary processor to develop sheet film, and after a little modifying of the spirals I am really happy with the results. I make up ID-11 from raw chemicals and this gives really tonally smooth negatives, not at all dense or contrasty. With subjects of a high contrast it's a brilliant method, but with subjects of a low contrast the negs can be a touch flat, and sometimes difficult to print, especially with semi-matt papers, and more especially with Forte paper. Developing the negs for longer only seems to increase density. Any suggestions as to how ID-11, or D-76 could be chemically tweaked to offer a touch more contrast with continuous development would be welcome. One option is to move out of northern England where the light is often flat - but the landscape is brilliant!

  2. #2
    Resident Heretic Bruce Watson's Avatar
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    contrast control with rotary processing

    Developing longer increases density, and contrast index (gamma). For a through explanation of how it works, see Ansel Adams book "The Negative." In it he explains how to determine development times to give both more, and less, contrast.

    Bruce Watson

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    contrast control with rotary processing

    Hi Richard,

    Get hold of a copy of "The Film Developing Cookbook", by S. Anchell and B. Troop. There are several solutions to your problem mentioned in the book. It is worthwhile reading.

  4. #4

    contrast control with rotary processing

    Richard.

    I too use a Jobo CPP2 for all processing of all sizes of films.

    I used D76/ID11 but changed to the Patterson Aculux2, which seemed to give me a contant contrast/tonal range that was easy to print.

    I have used Forte papers when printing misty scenes with good results, but have found that the Forte range can vary in contrast from batch to batch.

    I am sure that you could control the contrast in your Jobo using ID11. but feel it would be unwise to mess about with a tried and tested method of constant agitation, speed and time.

    Have you tried Kentmere VC or Ilford VC?

  5. #5
    Abuser of God's Sunlight
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    contrast control with rotary processing

    other options include:

    -higher developer temperature (no real advantages to this one)

    -higher developer concentration (will also give a straighter curve, if you happen to be looking for it)

    -higher concentration of alkali in the developer (seems to preserve the shape of your curve, and doesn't seem to increase grain as much as increasing development time.

    -selenium toning the negative (increases contrast but keeps other aspects of the neg identical. no good if you plan to intensify, etc.)

  6. #6
    Eric Woodbury
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    contrast control with rotary processing

    You can increase contrast (in the shadows) by increasing exposure and moving up away from the toe of the film. This works with many films, but if you already have plenty of exposure, then develop longer.
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    contrast control with rotary processing

    "Developing the negs for longer only seems to increase density."

    That's an interesting observation, as that is usually the answer to your question. I would suggest looking into the Adams book mentioned by Hogarth, or "Beyond the Zone System" by Phil Davis for a more in-depth treatment.

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    Abuser of God's Sunlight
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    contrast control with rotary processing

    "Developing the negs for longer only seems to increase density."

    I missed this the first time I read the post. Are you sure? I'd suggest testing it a bit more. It would be very unusual if increased development increased density EVENLY over the whole scale. If it worked like that, then you found a magical way to increase your film's speed. Typically what you'd expect is slight increase in density of the shadows (slight speed increase) and significant increase in density in the highlights (significant contrast increase).

  9. #9

    contrast control with rotary processing

    Thanks for all the interest in this one. I've read The Negative by Ansel Adams and in there he says (with images to back this up) that constant agitation leads to higher contrast. I once tried Agfa Rodinal with Jobo processing of FP 4 and the increase in contrast v intermittent agitation was quite alarming. ID-11 dosnt seem to work this way - it must be a chemical thing. Looking at some processed negs here, I can easily say there is an increase in density from over development for sure, and possibly greater shadow detail, but as for an expected increase in contrast - it isnt there. This is using 700ml of solution - ID-11 1+1 - 12 sheets for 7 mins. Altogether the negs are really smooth, although with a low contrast subject they can sometimes be 'muddy'. Perhaps I'll have to under-expose and over-develop although that goes against the grain a bit.

  10. #10

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    contrast control with rotary processing

    "I've read The Negative by Ansel Adams and in there he says (with images to back this up) that constant agitation leads to higher contrast."

    Yes, when compared to development that is not constantly agitated. You can still get lower levels of constrast with continuous agitation - simply use a shorter development time.

    Are you using your eye to make these density measurements? Perhaps you should look for access to a densitometer or make one with a spot meter.

    Again, I suggest checking into the Davis book I mentioned above.

    Kirk

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