Leader densities

Discussion in 'B&W: Film, Paper, Chemistry' started by Alessandro Serrao, Jan 11, 2017.

  1. Alessandro Serrao

    Alessandro Serrao Member

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    Hello everyone,
    this may be a dumb question but it's happening to me recently that no matter what developer I'm using, no matter what time I soup the film in, the leader comes out everytime with a not so bulletproof a density.
    I've got no scanner and no enlarger at the moment so I can't judge accurately since my eyes are not so trained.
    What kind of density should the leader have to say that a film has been properly developed?
     
  2. pdeeh

    pdeeh Member

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    You judge the quality of the negative by looking at the
    Exposed frames, not the leader. Surely?
     
  3. pentaxuser

    pentaxuser Subscriber

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    Alessandro, when my Xtol was more than 18months old I used to test it before developing a film. My method was to place the exposed leader in a small container of dev and then keep it there with some agitation for the time recommended for the actual film, then briefly fix and wash. If I could then look at the tungsten filament in a light bulb by holding the leader in front of the bulb and see it as a wire with none of the normal white intense glare I judged the leader to be of the right density.

    In every case this test, crude and unscientific as it may seem to be, gave me a film that was properly developed. I hope this helps

    pentaxuser
     
  4. OP
    Alessandro Serrao

    Alessandro Serrao Member

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    I must add that I prepare the d76 using distilled water. There are some threads on apug.org that basically say to avoid distilled water for all Kodak powder developers. Tap water is actually better. Who knows...
    Of course the frames are more important but the leader should tell me if the developer is active enough or if there's some other problems, right?
    I must add that all films I've developed are expired films stored at room temperature.
     
    Last edited: Jan 11, 2017
  5. Anon Ymous

    Anon Ymous Member

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    Alessandro, I've done what Peter said many times. I had many cases where you not only see the filament, but also the lamp itself and its surroundings, without any glare. The film was fine and both scanned and printed nicely.

    Regarding distilled water, I don't think it is something to be avoided, but just an overkill when preparing commercially packed D76. I won't hurt, but it's not needed either. If you were to scratch mix your D76 and not use a sequestering agent (like hexametaphosphate - tripolyphosphate), then you can easily end up with cloudy solutions because of water hardness. Distilled - deionised water would prevent this.
     
  6. ic-racer

    ic-racer Member

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    You would likely have to construct your D-max vs Gamma table from your own empiric data. This is because the shoulder (D-max) does not show on a typical 21-step wedge in the sensitometer. So you won't find see the shoulder (D-max) on most published film curve families. Remember, the densest values in the graph below are from the clear portion of the step wedge. The step wedge can't get any 'less dense' after the least dense step.

    [​IMG]
     
    Last edited: Jan 11, 2017
  7. piu58

    piu58 Member

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    The developer needs some time to build up the extreme densities. If your developing time is rather short it may be no enough time to develop the film let's say beyond a density of 2 or 1.8. If you are happy with your negatives, there is nothing wrong with it.
     
  8. ic-racer

    ic-racer Member

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    The density will be proportional to the development time and also to the gamma. Development time can't be 'too short' unless you get, no density in the film.
     
  9. OP
    Alessandro Serrao

    Alessandro Serrao Member

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    Let me just for one second divert from the actual topic.
    What kind of direct relationship is there between age of the film and DMax achievable?
    In other words: for every year of expiration, how much must I compensate the exposure?
     
  10. Photo Engineer

    Photo Engineer Subscriber

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    Back to the original post, a leader can be so overexposed that with some films it is "solarized" and begins to reverse, thus losing density. However, development is usually the culprit.

    PE
     
  11. georgegrosu

    georgegrosu Member

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    There are several ways you can interpret photographic results.
    Usually test stripe is the thing that tells you if the processing was good.
    The test stripe must be exposed on film you work to be most accurate information.
    For me, it is the most reliable.
    If you have not a test stripe, analysis the negative is a way.
    Here it is embedded film (age, exposure) and processing (developer state and time / temperature).
    I would not extrapolate the results of a test for all films who are on earth, especially if it is a bit old.

    George
     
  12. RalphLambrecht

    RalphLambrecht Subscriber

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    good question but answer unknown and most likely changes from film to film and dev to dev. You could easily make a research paper out of this with unfortunately few people interested in the results given today's film usage.
     
  13. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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    I would think that since the leader is not exposed by an exact and known amount of light, it would be useless information.
     
  14. Gerald C Koch

    Gerald C Koch Subscriber

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    It's not unusual that the leader of fully developed fine grained films will appear transparent. In other words you can see detail when looking through it. This does not mean that the film is incompletely developed.
     
  15. georgegrosu

    georgegrosu Member

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    “Alessandro Serrao said:

    Let me just for one second divert from the actual topic.
    What kind of direct relationship is there between age of the film and DMax achievable?
    In other words: for every year of expiration, how much must I compensate the exposure?
    good question but answer unknown and most likely changes from film to film and dev to dev. You could easily make a
    research paper out of this with unfortunately few people interested in the results given today's film usage.

    Ralph W. Lambrecht „

    Some years ago I was concerned about the mathematical description of the process of films.
    Photochemical development process can be described by a formula, I as similarity theory:
    VRt = A • ta • Db • Cc
    - VRt = rate of reaction in the process of development (mol / min) at time t;
    - A = constant;
    - Developing time t = (min.);
    - D = diffusion components (m2 / min.);
    - C = concentration of substance (mole / m3);
    - a, b, c = exponents.
    Writing dimensional equation, we have:

    From this equation, it follows that the greatest importance to developing photochemical process has diffusion.
    Temperature is a parameter that influences the diffusion. It must not forget the agitation of the developer.
    Development time has a lower contribution being the 1/2 power.
    On the other hand, I wanted to connect this reaction speed with sensitometric readings (density).
    VRt = k • Densitate
    where:
    - VRt = The reaction speed of the development process (mol / min) | at time t;
    - k = constant of the process at time t of the process;
    - Densitate = density obtained from the processing film at the time t.

    George
     

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  16. ic-racer

    ic-racer Member

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    That is why the leader is used. Unless solarized (as PE noted) additional exposure does not increase density. So, how much exposure the leader got, does not matter.