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  1. #21

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    Kodak has several technical information web pages on both cine and still films, which state that nothing (including freezing) stops cosmic radiation from fogging film. Faster films are affected to a greater extent. And modern T-grain emulsions (like Acros and Delta) having a lower D-max, are less able to overcome this fog.

    One of these Kodak technical pages can be found at:

    http://www.kodak.com/global/en/consu...fo/e30/e30.pdf

    There are several others scattered around if you do an extensive web search.

  2. #22
    Ed Sukach's Avatar
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    Quote Originally Posted by John Cook
    Kodak has several technical information web pages on both cine and still films, which state that nothing (including freezing) stops cosmic radiation from fogging film. Faster films are affected to a greater extent. And modern T-grain emulsions (like Acros and Delta) having a lower D-max, are less able to overcome this fog.One of these Kodak technical pages can be found at:
    http://www.kodak.com/global/en/consu...fo/e30/e30.pdf
    There are several others scattered around if you do an extensive web search.
    That was interesting, but not really very enlightening.

    "While storage in a refrigerator or freezer can be highly beneficial, you should not rely on it to extend film life beyond the "Develop Before" date. This is especially important with high speed films, which can be fogged by cosmic and gamma radiation that is naturally present all around us. Neither cooling nor lead-foil bags will prevent this effect."

    - This seems to equate Gamma Radiation with the higher energy "cosmic" radiation.

    Again in my role as questioner: If there is no extension of life "to be relied on" from lowered temperature, just how is there a "highly beneficial" effect?

    - Or am I to accept all information from Great Yellow Father to be gospel truth as a matter orf faith ... something I have learned not to do - largely from lessons taught by Kodak?

    What would really be necessary is objective information about the strength of potentially damaging background radiation, and definitive result from some sort of controlled study relating to film longevity.
    A few hours - something more than that - of Google - and others - searching has been unsuccessful.
    Carpe erratum!!

    Ed Sukach, FFP.

  3. #23
    Donald Qualls's Avatar
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    Quote Originally Posted by Jeremy Moore
    So, Donald, you are saying that keeping 900 sheets of Efke PL100 in the freezer while I use them over the next couple of years is no problem at all....
    I wouldn't expect any problem at all, as long as it isn't already expired and hasn't already been stored at 120 F for a prolonged time...
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  4. #24
    Donald Qualls's Avatar
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    Quote Originally Posted by Ed Sukach
    I don't mean this as sarcasm, but I hope you have noticed that at times there is a WIDE gap between theory and practice - not that the theory is flawed, but that we cannot envision every factor that can possibly affect any given outcome.
    I can understand this.

    Unfortunately, a) I haven't tested this and am not a physicist who could give quantitative arguments based on hard theory, b) I don't know of any genuine testing that's been done that's specific enough to be very helpful. There are so many variables involved that the only really useful test for what we're discussing would be to take a bunch of film from the same batch, shipped as a unit, and stick it all in the same freezer, then pull some out every year or two, expose a portion on a step wedge, and develop in freshly mixed published-formula developer (ideally, in multiple separately mixed batches of that developer, or even in different formulae to avoid a systematic error due to a manufacturing change in an ingredient). It should be obvious, by now, why it hasn't been done.

    I think you're right, in that we can assume that harder radiation will have more effect, and it's well known on a general basis that faster films are more affected (just as they are by a given amount of visible light). For film fogging purposes, it's not at all unreasonable to equate gamma with cosmic ray cascade products.

    I just don't think the hard data on how much effect there is really exists at all -- not even inside Kodak. We can only go by rules of thumb: more radiation is bad (don't let your film get x-rayed more than absolutely necessary, don't store it on a mountaintop above 70% of the atmosphere, don't store it in a pitchblende mine or a basement with known radon accumulation), and harder radiation is worse (dental x-rays aren't anything like as bad as gamma, in terms of penetrating packaging or in terms of amount of exposure to the halide). Faster films are more affected, and those with lower reciprocity failure likewise. And cold storage won't stop radiation induced fogging, though it does a very good job of retarding thermal based chemical degradation.
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

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