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  1. #11
    Photo Engineer's Avatar
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    Epitaxy on cubes

    Roger;

    Here is a picture of epitaxial growth on a cubic emulsion.

    Originally, it was a technique developed for making high speed chloro-iodide emulsions for color paper. IDK if they ended up using them, but I know a lot of work was done on this.

    Hope this helps.

    Photo by T. Shiozawa courtesy of Bruce Kahn, blurring by me.

    PE
    Attached Thumbnails Attached Thumbnails epitaxy.jpg  

  2. #12

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    Quote Originally Posted by Photo Engineer View Post
    Roger;

    Here is a picture of epitaxial growth on a cubic emulsion.

    Originally, it was a technique developed for making high speed chloro-iodide emulsions for color paper. IDK if they ended up using them, but I know a lot of work was done on this.

    Hope this helps.

    Photo by T. Shiozawa courtesy of Bruce Kahn, blurring by me.

    PE
    Dear PE,

    I'm pretty sure that the Delta grains are epitaxial on a triangular crystal (hence Delta) but as I say I can't find the EMs. Frances thinks she can but hasn't got around to it yet -- it was her birthday yesterday so she wasn't working. I am reasonably familiar with EMs of epitaxy but, of course, for me it's only an idle interest because I'm not designing the stuff. Thus I paid less attention than you might to the EMs which I saw some years ago and can't find.

    Cheers,

    R.

  3. #13
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    In Photographic Sensitivity Tadaki Tani mentions epitaxial grains, and he does show the above EM of AgCl cubic host grains with eight epitaxial (AgBr(Cl)) guest grains at the corners. He cites Joe Maskasky, as already mentioned by PE, along with T Sugimoto and K Miyake of Fuji, and a google on those two names together will turn up some references.

    Best,
    Helen

  4. #14

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    Dear PE et al,

    I will get our head of R&D to reply.....technically you are way out of my technical league....

    Simon ILFORD Photo / HARMAN technology Limited

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    Perhaps with some electron microscopy images of our little DELTA CG crystals

    Simon

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    what about mixing gray crystals of various shades in there and getting an analog film? wouldn't it allow for less grain? black and white, and gray hurray!

  7. #17
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    Quote Originally Posted by cotdt View Post
    what about mixing gray crystals of various shades in there and getting an analog film? wouldn't it allow for less grain? black and white, and gray hurray!
    I'm sorry, but I guess I don't understand the question.

    That is an analog film.

    PE

  8. #18

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    Quote Originally Posted by Photo Engineer View Post
    I'm sorry, but I guess I don't understand the question.

    That is an analog film.

    PE
    i meant that B&W film is digital, because on the microscopic level everything is black and white. wouldn't it be better to utilize analog technology like digital sensors, where you can have grays? would that improve ISO performance?

  9. #19
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    Quote Originally Posted by cotdt View Post
    i meant that B&W film is digital, because on the microscopic level everything is black and white. wouldn't it be better to utilize analog technology like digital sensors, where you can have grays? would that improve ISO performance?
    I think I get what you are referring to. I guess 'stain' left in the emulsion would have this effect.

  10. #20
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    Quote Originally Posted by cotdt View Post
    i meant that B&W film is digital, because on the microscopic level everything is black and white. wouldn't it be better to utilize analog technology like digital sensors, where you can have grays? would that improve ISO performance?
    You can have grays here as well, if only part of the grain is developed. So, if you take a 'sensor' sized piece of the processed film you have an equivalent gray to a sensor. One is revealed by Density and the other is revealed by Voltage. Both are analog values BTW. The analog value is converted to density by a computer program.

    On a micro and macro scale, you get an D LogE and a V Log E scale respectively. These form equivalent images.

    Since the actual speed is determined by a grain of silver, the ISO speed is effectively set by grain size. Bigger grains give higher ISO. More development means greater density and varying shades of gray. The fact that the sensor is larger and set side-by-side gives higher grain, lower detail and aliasing which you don't get with film.

    PE

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