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  1. #11
    ic-racer's Avatar
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    Quote Originally Posted by Rudeofus View Post
    write about the shoulder and the importance of its shape,
    The shape of the shoulder is of no importance if there is no image forming data there. What are you taking pictures of that places density way out there? Light sources?

  2. #12
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    Quote Originally Posted by ic-racer View Post
    The shape of the shoulder is of no importance if there is no image forming data there. What are you taking pictures of that places density way out there? Light sources?
    Here:

    Quote Originally Posted by Rudeofus View Post
    There are some situations where I would really like to know in advance how certain films are going to respond to severe local overexposure, e.g. any scene including the sun during broad daylight or any scene including the moon at night.
    Trying to be the best of whatever I am, even if what I am is no good.

  3. #13
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    Quote Originally Posted by Photo Engineer View Post
    If you look at a standard H&D curve, for negative films the shoulder is on the right where the straight line ends and density levels off.
    Yes, and unfortunately only very few characteristic curves posted in data sheets show that shoulder. If you look at the curves Michael posted (and the like of which can be found in most data sheets), the curves suddenly end in the straight section with no shoulder in sight.

    Quote Originally Posted by Photo Engineer View Post
    Usually, this is about D=3.0 but in negative films and MP print films it can be higher or it may not even be present due to extreme latitude.
    You mean the film goes up in flames if you expose it more? At some point all the silver must be activated and reduced by the developer, so there must be some form of well defined shoulder in every negative film.
    Trying to be the best of whatever I am, even if what I am is no good.

  4. #14
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    Quote Originally Posted by Rudeofus View Post

    You mean the film goes up in flames if you expose it more? At some point all the silver must be activated and reduced by the developer, so there must be some form of well defined shoulder in every negative film.
    This is not actually correct. Films can be designed to have a straight line up to densities of 6.0 or greater, but they are never needed in practice. A density of 3.0 - 4.0 is generally enough and the curves posted generally encompass enough latitude for overexposure by as much as 2 stops. As you push into the shoulder, you lose detail, of course. The same is true of the toe. Neither can be totally eliminated.

    Sometimes more detail is lost by the printing process than by overexposure of the negative, and this can only be corrected by creative printing (split grade printing and / or dodging and burning)

    PE

  5. #15
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    I'll explain what I have done in more detail. I have a 21 step wedge that is over twice as wide as my densitometer aperture. I cover 1/2 of the step wedge with a strong ND filter so that I am left with 42 boxes, each slightly larger than my densitometer aperture. I use that to make the exposure.

    However, there are technical hurdles. For example you need very tight contact or else it bleeds too much from the strong light needed to make the exposure. The soft foam of an EG&G is not enough pressure.

    Also, the exposure duration needs to be much longer than one would use for a H&D curve made with a 21 step wedge, so you may need multiple pops of the sensitometer flash, thus straying from the realm of any presumed ISO testing condition.

    Another way to put it is that with a sensitometer calibrated for ISO testing, the light may not be strong enough to get the film to the shoulder even without any added density. You understand that the last step of the wedge is clear, so you can't just make it "more clear" if you know what I mean.

  6. #16
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    So what you say is the characteristic curve published in the data sheet is meant for the zone system disciples who need 10 stops and no more, so the curves show a little more than that to cover exposure errors. It also appears that film goes way beyond the density range shown in these curves but much higher densities would require multi mega watt enlarger lamps (log10 is one flat curve).

    Thanks all for the clarification!
    Trying to be the best of whatever I am, even if what I am is no good.

  7. #17
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    No, I did not say that! I did not mention the zone system and we never used it at EK AFAIK.

    The curve as you see it is normally truncated at about D= 3.0 because that is what is normally used. Also, it might be that the normal curve that goes higher than that is larger than a sheet of 8.5 x 11" paper that we use for plotting. In fact, I have drawn larger curves horizontally by taping 2 sheets together.

    But, what is on the shoulder does not matter as D=3.0 for example and is unchanged. On the shoulder itself, you can modify it during printing as I noted above.

    But, as you say, it is mainly due to the fact that at extremely high densities you have, as you say, long printing times or bright bulbs!

    Again, the zone system is not really involved here.

    PE

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