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  1. #101
    Hexavalent's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Now, as to the question, the dyes adsorb at their preferred ratio if you add them to the emulsion. Since you stir, the dye is distributed and used up at the proper amount for each grain size. ...

    And, I would add that your method would work if there was an excess of dye, but you would also change the vAg of the emulsion thereby changing its surface adsorption characteristics. It would therefor cause some sort of secondary problem IMHO.

    PE
    I was wondering about this myself, and thought that post-dye washing might lead to a whole new set of variables. There IS a method to the madness
    - Ian

  2. #102

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    PE,
    Sorry about the dye/pigment confusion. Must have head in two different places at once. "Back in the day" I worked with pigments, not dyes.
    Bil

  3. #103

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    Quote Originally Posted by Kirk Keyes View Post
    If a diffraction grating is used in the design of a recording spectrograph, then care does have to be taken to eliminate 2nd order diffractions so that they do not show up when trying to measure a 1st order diffration. The second order pattern will be at 1/2 the wavelength of the 1st order, and when trying to record wide ranges of wavelengths, it can be a big problem.

    It's not an issue if a prism is used.

    It's not an issue either if a thick (holographic) grating is used that largely suppresses higher diffraction orders.

  4. #104

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    Quote Originally Posted by Hologram View Post
    It's not an issue either if a thick (holographic) grating is used that largely suppresses higher diffraction orders.
    Are you sure? diffraction orders are part of the nature of diffration gratings. It's the overlap between the 1st order and 2nd order that comes into play when trying to record a wide range of wavelengths. If you are trying to measure upto 900 nm in the IR with a 1st order diffraction, the second order diffractio for 900 nm will start to overlap at 900/2= 450 nm, which is where you are trying to record blue wavelengths.

    We don't even have to worry about 3rd and 4th order diffrations, as they will overlap starting at 300 nm and 225 nm respectively.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  5. #105

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    Quote Originally Posted by Kirk Keyes View Post
    Are you sure?
    Yes (sorry for the late reply), with a thick enough volume holographic grating you can suppress higher diffraction orders.

    To get back to AgX spectral sensitizers, here's another link: http://www.organica.de/en/Products/49,Functional_Dyes

  6. #106
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    03910 and 03930 look like possible candidates. Look for structures like those but with less steric hindrance.

    PE

  7. #107

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    Hello Ron and All,
    Recently, I have been working with an emulsion that is higher in I:Br ratio than I have worked with previously. As I have written here befor, I work with Ron's suggestion of DSA3057 (red senisitizer due to J aggrigates) and SDE 3008(green sensitizer). By total accident, I have found that the SDE3008 is acting as both a green and red sensitizer. Also the degree of sensitivity to all 3 colors is very even. There are several differences between this emulsion and what I have worked on befor. And, like all of my emulsions, it uses silane treated PVA instead of gelatin. But the latter could NOT be the reason for the accidental Red sensitivity, as I have been working with silane treated PVA emulsion almost as long as I have been working with emulsions.
    There is another R&G sensitizer , or so I am told, that I will also be trying
    I have slowed down lately and will be taking a "leave of absense" from "wet work" for 6-8 weeks due to upcoming surgery. But right now, I am taking the above emulsion, which I HAVE been able to replicate and scale up, and try to improve the coating chracteristics. As of now, containing no sufactant at all, it leaves random craters when coated onto very clean glass.
    Best of luck to you all,
    Bill

  8. #108
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    Thanks for the update Bill. The behavior that you see is not unusual. It is probably due to Iodide concentration on the different grains, or on the absolute concentration. If it is the latter, then the sensitivity will gradually shift towards being all red if you up the concentration slightly. But, OTOH, either mechanism is ok. It really does not matter. Repeatable success is what counts.

    Best wishes on the surgery and may your recovery be swift and complete.

    PE

  9. #109

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    Examples

    Thanks,PE-Here are two examples. When you judge the coating quality, please remember that I am working in total darkness with only a cheap night vision monicle to see with. I cannot realy see my coating until after the fix. The glass plates were exposed at f11 for 1 and 10 seconds.
    Attached Thumbnails Attached Thumbnails 2-24-12 ortho.jpg   2-25-1 SECOND.jpg  

  10. #110
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    Thanks Bil.

    Who am I to complain. I hide all of my bad coatings in a big big box. Believe me, I know how hard it is.

    PE



 

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