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  1. #51

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    I read somewhere else that the poor man's way of making a spectroscope is to use the silvered surface of an ordinary CD as a diffraction grating. Never had the urge or need to try it but they do reflect a rainbow effect in certain light. For what it's worth. OzJohn

  2. #52
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    John, that's a great idea. I do recall seeing some DIY spectroscope before. (here it is)

    The design would obviously have to be a bit different than this example since you'd want to have a reference light source and to project the spectrum onto a film sample. I would think that if you're messing around with spectral sensitizing you'd really want to have some way to qualify what you're doing.

    Ron, who made monochromators designed for this kind of thing?

    Maybe we should make Bill one so he doesn't have to keep pounding his pud all day...

  3. #53
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    Now all you need is a step wedge perpendicular to the horizontal spectral lines.

    PE

  4. #54
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    I thought the idea was that you projected them obliquely onto a surface and the spectral beams naturally decrease in intensity as they travel, no step wedge needed.

    Or a step wedge works too.
    If you are the big tree, we are the small axe

  5. #55

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    Holmburgers,
    Seeing a spectrum is one thing. Reading-interpriting one is another. I know from first hand experience that one can get so caught up in analysis that you frind yourself doing nothing but analysis. An organized multi-person effort is about the only way to go here. I have known photographers who do nothing but curves on graph paper. Thats fine. It obviously makes them happy. So, I let you make the spectrometer. Then I will send you samples to read!
    Bill

  6. #56
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    Quote Originally Posted by holmburgers View Post
    I thought the idea was that you projected them obliquely onto a surface and the spectral beams naturally decrease in intensity as they travel, no step wedge needed.

    Or a step wedge works too.
    Nope. You need a step wedge. You also should know the frequency in nanometers if you are to read a B&W spectrogram. With color, it is a bit easier.

    PE

  7. #57
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    Well well... that's ok Bill.

    Maybe instead of quantifying the results, we should be content with qualifying them. I would think that by comparing one emulsion to a manufactured film you could tell a lot from that. A piece-of-junk shoebox monochromator might be surprisingly illuminating (that's not a pun), and building it sounds like not a bad way to spend an afternoon either.

    But anyways, I'm not about to go testing emulsions when I get home, I'm just enjoying the discussion.

  8. #58
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    I made such a contraption (shoe box, grating etc.,) many many moons ago based on a "Amateur Scientist" article in Scientific America. (You might find the article in a web search). IIRC, I used a grating from Edmund Scientific.
    Of course, for any real accuracy, one needs to know the profile of the light source and all the optics.
    Last edited by Hexavalent; 10-26-2011 at 03:54 PM. Click to view previous post history. Reason: grammar eh!
    - Ian

  9. #59

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    One of my many unfinished projects is to make a recording spectrograph for testing films/emulsions. I've got a really beautiful 3" concave diffraction grating waiting for the project.
    Kirk

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

  10. #60

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    Quote Originally Posted by holmburgers View Post
    This is a completely foreign language to me, but I'd like to learn it. What do you call these kinds of diagrams?
    You're going to U Kansas aren't you? You should sign up and take General Chem and the Organic Chem. Don't think of it as two long years of work, just think of it as a great way to learn more about an aspect of emulsion making!

    I'd say the problem with the Rhodamines is that oxygen molecule right in the middle of the molecule. The cyanines have carbon atoms that are conjugated (google it) between the nitrogens. It's that conjugation that allows the dye to have electron resonance and be good dye. The oxygens don't allow the resonance as well being in the middle of the chain of conjugated carbons.

    I believe (PE correct me if I get it wrong) it's the electron orbitals projecting up from the nitrogens on the ends of the cyanines are the source of the electrons for the resonance and also allow the dye to attach to the silver halide crystal.
    Kirk

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



 

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