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  1. #21

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    Quote Originally Posted by markbarendt View Post
    Good thoughts Doremus.

    One thought/question though here;



    Isn't compensation more about fitting the scene to the paper by encouraging the film curve to shoulder off by discouraging highlight development?

    Seems to me that compensation is actually "designed" to get to more print detail by actually reducing the negative's highlight detail.

    Put another way, isn't compensation simply trying to create more of an S-curve than a linear curve?
    Correct, Mark. The total "information" that can be in the negative is limited by the film's inherent exposure scale, and exposure. Development can either maintain that information, or reduce it. It can not increase it. Compensating development preferentially reduces highlight contrast. Highlight information is "expensed" for easier printing.

  2. #22
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    I remember reading somewhere that with proper exposure, compensation can also be used to improve local contrast in the mid-tones, especially for portraits.

  3. #23
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    Quote Originally Posted by kintatsu View Post
    I remember reading somewhere that with proper exposure, compensation can also be used to improve local contrast in the mid-tones, especially for portraits.
    Compensation reduces contrast so...
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  4. #24

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    The OP is proposing using a fixed number of agitations instead of a fixed time-interval.
    My knowledge of chemistry is rudimentary, but this makes perfect sense to me.
    If a chemical reaction only proceeds half as fast and thus takes twice as long, then doubling the time-interval (giving the same number of agitations) will produce the same result as double-speed and half-interval.

    However, the rate of diffusion through gelatin does not depend on dev-rate, so that complicates things.

    Anyway, I have created a concentrate giving XTOL-quality, and I designed it to have twice the dev-time as XTOL. And I recommend agitating every 60 seconds instead of Kodak's recommendation of every 30 seconds. It's worked fine in my experiments.

    Mark Overton

  5. #25

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    Has anyone mentioned "diffusion" yet? (Doremus used "infuse"...)

    The reason for agitation has little to do with chemical "reactions" but a lot to do with helping the chemicals diffuse into the gelatin matrix of the film. The agitation ensures that fresh developer solution is brought into physical contact with the surface of the gelatin so that fresh developer gets into the gelatin and it helps remove development byproducts from the gelatin faster than if there was no agitation.

  6. #26

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    Quote Originally Posted by markbarendt View Post
    Good thoughts Doremus. One thought/question though here;

    Isn't compensation more about fitting the scene to the paper by encouraging the film curve to shoulder off by discouraging highlight development?
    Seems to me that compensation is actually "designed" to get to more print detail by actually reducing the negative's highlight detail.
    Put another way, isn't compensation simply trying to create more of an S-curve than a linear curve?
    Quote Originally Posted by Michael R 1974 View Post
    Correct, Mark. The total "information" that can be in the negative is limited by the film's inherent exposure scale, and exposure. Development can either maintain that information, or reduce it. It can not increase it. Compensating development preferentially reduces highlight contrast. Highlight information is "expensed" for easier printing.
    Although I'm no sensitometrist, I believe that, yes indeed, the effect of compensating development is to shoulder the film curve a bit. Since the amount of actual compensation, i.e., the comparative reduction in density, is greater where the developer exhausts sooner, which is in the areas of highest exposure. The change is progressively less in lower-density areas until the point is reached below which no developer exhaustion at all occurs. This reduces highlight contrast, but allows a very bright area to still be printed which, without compensation, would be "blown out" or off the paper's scale or need burning.

    Still, in my book this means being able to get (squeeze) more usable information into the printable density range of the negative. It's really a question of semantics.

    Best,

    Doremus

  7. #27

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    Quote Originally Posted by markbarendt View Post
    Compensation reduces contrast ...
    ... more in the highlights than in the low and mid-tones. And, if the compensating effect null-point, i.e., the point of exposure below which no compensation takes place is fairly high on the film's curve, you can effectively increase mid-tone contrast, reduce highlight contrast above that and thus "enhance" shadows and midtones. This, of course, in comparison to a negative developed without compensation and where the highlight points are matched.

    Best,

    Doremus

    www.DoremusScudder.com

  8. #28

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    Quote Originally Posted by albada View Post
    The OP is proposing using a fixed number of agitations instead of a fixed time-interval.
    My knowledge of chemistry is rudimentary, but this makes perfect sense to me.
    If a chemical reaction only proceeds half as fast and thus takes twice as long, then doubling the time-interval (giving the same number of agitations) will produce the same result as double-speed and half-interval.

    However, the rate of diffusion through gelatin does not depend on dev-rate, so that complicates things.

    Anyway, I have created a concentrate giving XTOL-quality, and I designed it to have twice the dev-time as XTOL. And I recommend agitating every 60 seconds instead of Kodak's recommendation of every 30 seconds. It's worked fine in my experiments.

    Mark Overton
    Mark,

    Just a couple of thoughts here:

    First, the time between agitations is long enough to allow the developer to exhaust in areas of greater density (compensation) should be fairly constant for a given film/developer combination.

    Now, if you want a compensating effect, you need to make sure the time between agitations is long enough. It would seem to me that this time would be longer with a more active developer than with a less active/weaker one. Therefore, to achieve a certain amount of compensation, one would have to increase the agitation intervals for the more active developer, not decrease them as the OP is suggesting.

    Similarly, for weaker developers, the interval at which a certain amount of compensation occurs will be shorter. Therefore, for a given amount of compensation, one would have to increase the frequency of agitation compared to a more active developer, not decrease it.

    Of course if you don't want and compensation, then just agitate away, it shouldn't make much difference at all as long as the agitations aren't long enough for developer to exhaust in the highlights; any agitation scheme that accomplishes this would yield the same results as long as development time was appropriately adjusted.

    Best,

    Doremus

  9. #29

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    Quote Originally Posted by Kirk Keyes View Post
    Has anyone mentioned "diffusion" yet? (Doremus used "infuse"...)
    ... and should have used "diffused." Although the "stronger" less-exhausted developer in a low-density area moves into a bit of the area of higher density much like tea infuses into hot water, I think the better technical description would be "diffusion from areas of high concentration to lower," or something like that. I stand corrected.

    Best,

    Doremus

  10. #30
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    Quote Originally Posted by Doremus Scudder View Post
    Still, in my book this means being able to get (squeeze) more usable information into the printable density range of the negative.
    The point I see many people miss is that the paper defines the range that prints straight and easy from the negative.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

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