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  1. #11
    Photo Engineer's Avatar
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    Keith;

    With a blue sensitive only emulsion, in the first row of the figure, it is difficult to say, but in the remaining examples, you see how the sensitizing dye represses blue sensitivity? In those cases, a blue sensitizing dye would have left its trace as a distinct peak in the range I gave. It would show up more clearly. So, in full answer, to #1, IDK, to the rest, most likely no blue sensitizer, just native remaining blue sensitivity.

    I'll qualify that by adding that the last row example may have a blue sensitizer. Note the increase in peak?

    PE
    Last edited by Photo Engineer; 04-14-2009 at 01:55 PM. Click to view previous post history. Reason: Added last sentence

  2. #12

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    Quote Originally Posted by Photo Engineer View Post
    ...the last row example may have a blue sensitizer.PE
    One thing is curious in that last one...

    the sensitivity seems to suddenly cut off somewhat unnaturally (on both ends but esp.) at about 675 or so.

    Do you think this is an artifact of some sort ?

    Ray

  3. #13
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    Ray;

    At least 2 if not 3 monochromators would have to be used for those IR exposures. There would be one more if UV was required. In the manipulation, I'm sure artifacts would apppear. My spectrosensitometer can do that type of exposure, but it must be in 3 stages with a reset and recalibration of the device after each separate exposure.

    Picky, picky, picky!

    This is the nature of many such spectral devices. In fact, in the far IR case, glass cannot be used in some cases. We used cast Sodium Bromide crystals. They were about 1/2" square, about 1/4" thick and cost more than some people make in a year. They had to be stored in a vacuum dessicator while not in use.

    PE

  4. #14
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    Yup that looks like there was a lamp change. To take these data, one would ideally have a lamp with relatively flat output across the wavelength range, but that was basically impossible to get across the whole range from UV to IR. Now you can do it with a really good white light source e.g. a Ti:Sapphire laser pumping a photonic fiber, which they most assuredly did not have when this data was taken. Back then I guess they would have switched lamps, corrected the relative intensities for the lamp spectra as best they could, and just stitched the different wavelength regions together... probably with a copier machine and some tape
    "Only dead fish follow the stream"

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  5. #15
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    Just so Keith. The monocrhomator and the power supply have settings on them to do just as you describe.

    PE

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