Physical Development - Fine grain from fast films??

Discussion in 'B&W: Film, Paper, Chemistry' started by holmburgers, May 9, 2011.

  1. holmburgers

    holmburgers Member

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    Looking through Wall & Jordan's Photographic Facts & Formulas, I came across a comment about physical development which is very intriguing.

    "It results in a very fine grained image, regardless of the size of grains in the emulsion."

    This makes sense, knowing that in physical development the silver is deposited/supplied from the developer solutions, not the emulsion silver itself.

    Quote, "In this process a silver salt is combined with a reducing agent in the developer, and the action is to precipitate silver on the latent image, rather than to reduce the silver in the emulsion as is done bye chemical development."

    What seems most intriguing is the prospect of physical development of fast films; the 400 speed films of course, but better yet the 3200 variety.

    The book mentions some difficulties, such as the contrast of the negative cannot really be affected, which might suggest that pushing is not an option. Furthermore, the process itself sounds quite critical and requires silver nitrate. Furthermore-more, another section which addresses physical development of lantern slides says that speed is cut in half, though this is a different formula as well.

    All told though, I'd love to see what could be done. What would fine grained Delta 3200 look like?? Anyone ever done this, seen it or feel like doing it?

    :D
     
  2. Ian Grant

    Ian Grant Subscriber

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    Unfortunately it doesn't work with modern emulsions and would result in an enormous loss of speed. However there's a very small amount of physical development in developers like D76/ID-11 where the high Sodium Sulphite level acts as a weak silver solvent, this helps to reduce the films graininess.

    Ian
     
  3. holmburgers

    holmburgers Member

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    Well that's a bummer!

    Ok, the inevitable question... why not? The book is a 1975 edition, was it a holdover from older times?
     
  4. Ian Grant

    Ian Grant Subscriber

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    It's been mentioned in many recent books more out of historical interest, in the case of Wall it's a carry over. One reference talks of some negatives for physical development needing 8 stops more exposure than normal. So that would take Delta 3200 to 12.5 EI :smile:

    Ian
     
  5. Vlad Soare

    Vlad Soare Member

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    One interesting thing about physical development is that it works even after fixing (but one must be very careful not to over-fix; rapid fixers are out of the question, because they dissolve the latent image).
    I understand that the biggest problems of this kind of development are the extreme loss of speed and the virtual lack of any contrast control. Another problem is, of course, the cost of the developer. Silver nitrate is not cheap.
    I'd like to try it once, just to see how it works. Ian, do you happen to have a formula for a suitable developer?

    No, no, yes. :smile:
     
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  6. holmburgers

    holmburgers Member

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    Thanks guys,

    Vlad, I can post the formula if you'd like (I don't have it with me at the moment). And yes, the fact that you can develop (by inspection) after fixation is quite interesting, if not altogether mind blowing. :D
     
  7. Vlad Soare

    Vlad Soare Member

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    Mees, in his Theory of the Photographic Process, describes this process very briefly. Only four pages out of one thousand are dedicated to it. :sad:
    He basically states that:

    1. The exposure must be approximately five times higher than in the case of chemical development. With high speed films it must be increased even more than that, so much more that it would generate a lot of fog. As this is the 1942 edition, I suspect that by high speed films he means ASA 200, or at most 400. :D

    2. Developing after fixation is preferable, because fixation will also reveal those latent image nuclei formed inside the grains, which are not accessible beforehand.

    3. Acidic fixers must be avoided, because they can dissolve the delicate latent image. Although he doesn't mention them directly, I assume that rapid fixers are totally out of the question for the same reason.

    4. Even basic solutions of sodium thiosulfate can destroy the latent image if they are aerated.

    5. The safest fixing agent is sodium sulfite, because it will never attack the latent image. However, sulfite cannot fix films with high iodide content.

    That's all he says about it. Hundreds of pages are dedicated to chemical development, and to developing agents, and only four to physical development. :sad:
    What I have is the 1942 edition. Maybe newer editions are more detailed; I don't know about that...
     
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  8. holmburgers

    holmburgers Member

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    Hmmm..... well I guess the basic premise of getting fine grain from Delta 3200 (and like the like) is out.

    :sad: *single tear*
     
  9. Trask

    Trask Subscriber

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  10. holmburgers

    holmburgers Member

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    Hey, that's a great link you've dug up!

    This sounds like something that I recently was told about holographic processing. I believe this kind of pseudo-physical development can be called "colloidal development", wherein the solvent liberates some of the silver halide and it is redeposited on the latent image.

    Did you ever give anything like this a go? I'd like to try it someday.