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  1. #21

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    Approx. 4 years ago Dr. Robert Chapman wrote an article on formate developments in b&w tedchnology..I may have mispelled that. This would allow approximately 2 stops of speed gain while not losing any other intrinsic quality. He guestimated that the fils would be hitting the market at about this time.

    Anyone know what is happening?
    Claire (Ms Anne Thrope is in the darkroom)

  2. #22
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    Formate development has been mentioned here before. It was done jointly by Agfa and a French researcher. This has not been commercialized.

    At the time, he didn't know about 2 electron sensitization coming from EK. So, he is right but for the wrong reasons.

    PE

  3. #23

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    Quote Originally Posted by Photo Engineer
    However, there are always tradeoffs in speed, grain and sharpness. For example, if you took an 800 film and doubled its speed using 2 electron sensitization to 1600, it may have worse keeping due to radiation (cosmic and heat), and so the tradeoff is to keep the same sensitivity to radiation at 800 speed and design for better grain. (this was hypothetical but appears to be the case for the new Portra 800).
    Radiation sensitivity is largely governed by the grain volume. If two-electron is applied, the efficiency of fog center creation will also increase, but if the crystals are made smaller, the overall shelf life may be comparable. Konica, who made true ASA3200 color negative films, did an extensive research on this topic and some results are published.

  4. #24

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    Quote Originally Posted by Claire Senft
    Approx. 4 years ago Dr. Robert Chapman wrote an article on formate developments in b&w tedchnology..I may have mispelled that. This would allow approximately 2 stops of speed gain while not losing any other intrinsic quality. He guestimated that the fils would be hitting the market at about this time.

    Anyone know what is happening?
    Check out the following US Patents:

    6,436,625 Photosensitive silver halide element with increased photosensitivity 6,344,311 Photosensitive silver halide element with increased photosensitivity 6,277,549 Photosensitive silver halide element with increased photosensitivity 5,985,536 Photosensitive silver halide emulsion containing a metal carbonyl-complex as a dopant

    The original idea was to dope the emulsion with formic acid, but this approach is not very practical outside a research lab, because it's not easy to incorporate formic acid into the grain and keep it there stably. So people have studied alternative ways to implement the same concept. Some appeared in patents, some appeared in scientific literature. They generally use some metal complex dopants.

  5. #25

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    Thank you both for your thoughtful response. PE I apologize for missing the previous posting.
    Claire (Ms Anne Thrope is in the darkroom)

  6. #26

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    Can't help the smaller format folk but if you are pining away for Pan X then get some Polaroid T55. It IS Pan X.

    As for EFKE (Adox) 25 it has always been a great film and if you have not tried it why not do so? In one form or another it has been around for some 50 years so there is really no reason to believe it is going to disappear tomorrow.

  7. #27
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    Quote Originally Posted by Ryuji
    Radiation sensitivity is largely governed by the grain volume. If two-electron is applied, the efficiency of fog center creation will also increase, but if the crystals are made smaller, the overall shelf life may be comparable. Konica, who made true ASA3200 color negative films, did an extensive research on this topic and some results are published.
    Exactly correct, but radiation generates ionized particles, and if electron efficiency increases, sensitivity to ionizing radiation goes up.

    At least that was why I made that hypothetical comment.

    I obviously have no way of determining why they chose an 800 speed film at better grain rather than a 1600 speed film at the grain of an 800 speed film. It could be other factors such as turbidity, sharpness or developability.

    PE

  8. #28
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    Lets see, I just bought a 1000 foot roll of 5" panatomic X. That should be good for...OH...3,000 4X5 negs. You'll just have to make the jump to 4X5 I guess. Oh and at 6½¢ each, they're a bargain. But they're a pain in the enlarger. The grain focuser is useless with them, you have to find an edge. There is no grain.
    He is no fool who gives what he cannot keep..to gain that which he cannot lose. Jim Elliot, 1949

    http://tonopahpictures.0catch.com

  9. #29
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    Quote Originally Posted by Claire Senft
    Panatomic=X was my favorite b&w film in 120 roll film, 35mm and sheet film. kodak did this user no favor in discontinuing it.
    Ditto that brother! And I want my Ektar 25 back, what I wonderful film.

    Don Bryant

  10. #30
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    Quote Originally Posted by donbga
    Ditto that brother! And I want my Ektar 25 back, what I wonderful film.

    Don Bryant
    I wish someone could directly compare Portra 100VC with Ektar 25!

    You might be surprised with the results in terms of grain and sharpness, not to mention color.

    PE

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