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  1. #71
    RobertP's Avatar
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    Red is rendered black. John had us shoot this to give us an idea of the sensitivity.

  2. #72
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    Ty, I hope it's monochromatic!
    Yep, that's what I was wondering about (blue sensitive). I was just curious if anyone had tried to 'shift' that at all.....
    Robert thanks for the photo with the spectrum (I had seen it earlier). Because of our earlier discussion on reversed images could you tell me what the color order is....?
    Gracias
    Scott

  3. #73
    RobertP's Avatar
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    I'm somewhat confused now myself I think it is L to R red to blue

  4. #74
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    Bromides extend the spectral sensitivity a little towards the green, but not much. There may also be an effect using different cations, but again it would be a small effect. Collodion is mainly UV and blue-sensitive, but a pure iodide emulsion will have less spectral sensitivity than one made with a bromide and iodide mix.

    It would appear that heavier cations (zinc, cadmium) give a little more spectral sensitivity than lighter ones (potassium, ammonium, sodium, lithium).

  5. #75
    RobertP's Avatar
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    Ok I got the loop out and read the bottom of the chart he is holding. It is a Kodak color control patches. So it isn't a blue to red spectrum. If you can find a 9 patch Kodak color control sample on line you will probably find the lighter patches the blue and violets. If you find one to compare match the patches in reverse. The one in this photo is reading right to left.

  6. #76
    RobertP's Avatar
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    I'll find a true color spectrum from blue to red and photograph it again. I'm curious now myself.

  7. #77
    schrochem's Avatar
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    I think it's kind of cool that you can change the spectral sensitivity (even if it's a little). Robert I think I found the color patch here. It's the second one.
    If I got that right then it would seem the photo you attached has gray on the right and blue on the left. But that would make the patch next to white (on the link I made that is magenta) be close to white???
    Thanks
    Scott

  8. #78
    RobertP's Avatar
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    Scott I don't think that is the right color patches. The reds should be rendered dark and the blues light. We didn't spend much time on this. And my old mind just can't recall the exacts. Next time I shoot I'll include a color spectrum in a shot and then a digital snap for you to compare. I don't want to mislead you.

  9. #79
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    No sweat Robert. That would be cool if you get around to it but no worries. The color patch was an older one (I believe) so the google fairy had a hard time finding one. However, I think this might be it. Well that is if the yellows go that dark and the magentas that light.
    Scott

  10. #80
    Ty G
    What is really "cool" is a tintype of a person with light blue eyes.

    Ty Guillory
    www.tystintypes.com
    Mineola, TX



 

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