Question about developer dilution

Discussion in 'Darkroom Developing and Printing' started by Robert J. Mathes, Aug 30, 2003.

  1. I would like to know what the effects are of developer dilution beyond the
    obvious of longer development such as does it affect grain size? Does it
    affect the action of the developer on the high or low values differently
    than straight developer? In other words, anything of significant importance
    gained through empirical observation. Thanks. All comments welcomed and
    greatly appreciated.

    bob mathes
     
    Robert J. Mathes, Aug 30, 2003
    #1
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  2. Which developer? The effects of dilution depend on the
    developer.
    Deveoping time does not vary linearly with dilution. For
    instance, diluting a developer to half strength results in
    an increase in time for the same contrast of about 1.5, not
    twice as one would expect. For developers which have a large
    amount of sulfite this can result in an increase in grain
    because some of the solvent action of the sulfite is lost.
    For developers with low sulfite and relatively poor
    buffering like Rodinal diluting will result in somewhat
    lower grain due to the lower pH.
    At some point diluted developers will start to produce
    border effects. This is the exageration of contrast at high
    gradient areas of the image, that is, where there is a sharp
    transition from low to high density. This is sometimes
    attributed to "local exhaustion" but that is not really what
    happens. As developers work they produce reaction products.
    These can either accelerate or restrain the development
    process depending on what the developing agents are and the
    amount of sulfite. In normal development the reaction
    products are limited by diffusion away from the area adn by
    diffusion of new developer to the area. Where the developer
    is sufficiently diluted there is not enough sulfite or other
    preservative components to limit the action so there is a
    tendency for the reaction products from the high density
    area to diffuse to the lower density area and interfere with
    development. Developers like D-76 will produced border
    effects, also called adjacency effects, when diluted 1:3.
    Developers like Microdol-X and Kodak D-25, which depend on
    strong solvent action for extra-fine-grain results lose
    their extra fine grain properties when diluted. They also
    gain some film speed since the loss of speed is due to the
    solvent action destroying some of the latent image. At 1:3
    these developers deliver grain and film speed about equal to
    D-76 full strength.
    For lesser dilution there may not be much effect. D-76 at
    1:1 has about the same grain and speed as full strength and
    doesn't have significant border effects.
    Very highly diluted developers, for instance Rodinal at
    1:200, can have compensating effects, that is, they stop
    development of high density areas causing a shoulder (or
    reduction of contrast) of the denser parts of the image.
    This is sometimes desirable where extrememly high conrast
    subjects have been photographed. This is again due to a
    build up of reaction products in the emulsion. The idea of
    stagnant or stand developing is similar. If the film is not
    agitated reaction products can move from the area of
    development only by diffusion through the developing
    solution. That is very slow compared to the rate of
    diffusion going throught only the emulsion as happens where
    normal agitation is applied. Stand development results in a
    somewhat distorted tonal renditon. It can also result in
    very uneven development if the film is vertical in the
    solution or there is any disturbance during development.
    When vertical there is localized movement due to convection.
    This can result in local directional streaking from denser
    reaction products. Eventually, they diffuse into the general
    body of the developer but remain in a cloud around the
    surface of the film for long enough to cause problems.
    In general reasonable dilution can result in more
    convenient development times and better uniformity without
    having much effect on other characteristics such as grain.
     
    Richard Knoppow, Aug 30, 2003
    #2
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  3. Robert J. Mathes

    hogarth Guest

    That's an involved question. Depends on the developer, film, temp, agitation....

    If you really want to know, I suggest you obtain a copy of Anchell and Troop's "The Film
    Developing Cookbook." They cover this topic in pretty good detail.
     
    hogarth, Aug 30, 2003
    #3
  4. Michael,

    I can't thank you enough for the information you've provided me about
    developer dilution. Your reply along with the information provided by
    Richard Knoppow (which was excellent and more then I had ever hoped for) has
    increased my knowledge and awareness of the effect of developer on film. The
    issue came up when I began shooting in large format (4x5) and looked to find
    information on development for the film used (FP4 sheets). The information
    on the box listed a time for development only for straight D-76 which I had
    been using for years with my roll films. I then realized how very little I
    knew about the action of developers in general and decided to set out to
    learn more. And posting to this newsgroup has been most rewarding!

    Again, at the risk of sounding too profuse, I want to thank you both for
    your response and the sharing of your knowledge and experience.

    Sincerely,

    bob mathes
     
    Robert J. Mathes, Sep 2, 2003
    #4
  5. Richard: You did not read carefully. Here's what I said: "The
    excess sulphite dissolves some of the image-forming silver salts
    as they are developing, producing a finer grain pattern."

    'Silver salts' are 'silver halides'.
    Yes, of course!
     
    Michael Scarpitti, Sep 2, 2003
    #5
  6. Used very little so far, was not sure developer was working properly.
    Negs very thin. No plans to try again. Acutol and FX-39 are my choices
    among prepared commercial products, also mix own.
     
    Michael Scarpitti, Sep 2, 2003
    #6
  7. Robert J. Mathes

    Alogenu®o Guest

    Negs very thin: it's true,I dont'know if it's better or no.
     
    Alogenu®o, Sep 2, 2003
    #7
  8. Robert J. Mathes

    Alogenu®o Guest

    Negs very thin: it's true,I dont'know if it's better or no.
    Which is the different with FX-39?
     
    Alogenu®o, Sep 2, 2003
    #8
  9. Robert J. Mathes

    Alogenu®o Guest

    My question is :
    which is the differenze than x-tol and Fx-39?
    Escuse me for the linguage.
     
    Alogenu®o, Sep 3, 2003
    #9
  10. They are different kinds of film developers. XTOL is from Kodak and FX-39
    is from Paterson. They work similarly, but every different developer has a
    slightly different result on each film.

    Jim
     
    Jim MacKenzie, Sep 3, 2003
    #10
  11. Robert J. Mathes

    Alogenu®o Guest

    Thanks again.

     
    Alogenu®o, Sep 4, 2003
    #11
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