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  1. #11
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    Quote Originally Posted by cowanw View Post
    This is very interesting.
    I am still of the opinion that the lighting of the body in the film image is not only uv lighting. The lighting must emit visible wavelengths. Indeed the image looks distinctly not blacklight and Quite ordinarily lit.
    I will be most interested in your further results
    Thanx for your interest.
    I have tried shooting it differently this time. To get rid of the UV-sensitivity of the film I shot one roll with a uv-filter on it. This helped in a way that the body turned out darker and the text seemed lit this time instead of nearly black/grayish. So that would explain the problem I was having.
    Still the image was way too light and killed the other light which was supposed to bring in some ambience.

    The second roll of film was shot using a green filter to have the red of the body filtered out, i.e. making it appear darker, and emphasizing the green of the lit text.
    This worked very well. All was actually perfect accept for it being to dark overall. I couldn't distinct the body from the background. The ambience was back and it resembled the digital photo much better.

    A day later I redid the shoot with 2 blacklights instead of 1 and again the green filter. I have to make contact sheets tomorrow but it's actually looking as I had it in mind so I'm fairly happy so far

    As soon as I have finished the contacts I'll post some examples in here for the ones interested.

  2. #12
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    I have scanned the contact sheets and they suck (the scans I mean). I will place them anyway to show what the difference in lighting does but it's by no means HQ huhum... Here we go:
    With UV-filter & 1 Blacklight:


    With Green-filter & 1 Blacklight:


    The testprint of the new version with greenfilter and 2 blacklight lights will be dry by tomorrow. I'll scan that one as well, which is going to give somewhat better qual than these scans and you'll see the effect even better. The green filter worked really great though I needed to shoot it with 2 blacklights as it took away a lot of the light.

  3. #13

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    Good problem solving.
    Am I right in presuming that, even thought you are illuminating the subject with UV light, what is being reflected off the subjects is always visible light? and the green filter has filtered out the skin tones and allowed the green of the paint to pass.
    The moniter in the back is a good measure of the consistency of your exposures.
    I still do not under stand the digital picture: it behaves as if it has the green filter on?
    Peculiar!
    "There are a great many things I am in doubt about at the moment, and I should consider myself favoured if you would kindly enlighten me. Signed, Doubtful, off to Canada." (BJP 1914).

    Regards
    Bill

  4. #14
    AgX
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    Bill,

    White skin reflects all wavelenghts from UV to IR. Though IR penetrates skin a bit and thus gives an image of deeper layers.

  5. #15

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    Yes, but the wavelengths passed by the green filter can only be that (visible) green wavelength. and the reflected illumination we see from a blacklight can only be visible wavelenths since we can not see UV.
    I am just having a difficulty putting together a general theory of illumination to explain all the OP's images.
    Can you help explain the 4 images?
    "There are a great many things I am in doubt about at the moment, and I should consider myself favoured if you would kindly enlighten me. Signed, Doubtful, off to Canada." (BJP 1914).

    Regards
    Bill

  6. #16

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    Not true. The green filter can be passing UV and IR, though from the images (and plots of filter transmissions) UV isn't being transmitted and it doesn't matter if IR is. And even though we can't see UV, film can. And just because film is sensitive to UV, doesn't mean a digital sensor is.

    For reference, here's the spectrum from a blacklight from wiki: spectrum.

  7. #17
    ath
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    Quote Originally Posted by cowanw View Post
    and the reflected illumination we see from a blacklight can only be visible wavelenths since we can not see UV.
    That's wrong. In these pictures you don't see the reflected light, you see what the film recorded from the reflected light. And film is UV sensitive.
    Regards,
    Andreas

  8. #18
    AgX
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    Bill,

    I admit I did not quite follow the discussio for a while, so I overlooked that green filter.

    Tim,

    That was my idea too, but I checked some charts and I did not find a green camera filter with UV transmission (though IR transmission).

    However, looking at some charts of green lighting filters, there are some with seemingly UV transmission.

  9. #19
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    So, here's an image from the second exposure with the green filter:


    From all I have seen now is that film is way more sensitive to UV than digital is. How to explain the text being close to black/grayish on the non-UV-filter photo stays kind of a riddle to me, maybe also because I'm just too tired to think about it now, I can merely take a guess.
    Anyway, the green filter did have the effect I had in mind.
    Thanx for all of your input

    Ow and this scan sucks as well as there's much more delicate detail in the shoulders and top of the body....sorry again for the lousy Q...

  10. #20

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    Quote Originally Posted by Tim Gray View Post
    Not true. The green filter can be passing UV and IR, though from the images (and plots of filter transmissions) UV isn't being transmitted and it doesn't matter if IR is. And even though we can't see UV, film can. And just because film is sensitive to UV, doesn't mean a digital sensor is.

    For reference, here's the spectrum from a blacklight from wiki: spectrum.
    Tim can you show why the green flter can be passing UV?
    I aways thought that the reason a filter was the colour it was, was that it passed only that wavelength. (of course nothing is perfect, not even B+W filters). Nevertheless, if a green filter passes UV and IR then it might reasonably pass deep red and deep blue, in which case it would not be a green filter.
    As to what the eyes see, I was kind of wondering which image most closely approximated the OP's actual eyeball view.
    Here is an interesting site concerning UV imaging, both film and digi. Note how the L37C uv filter completely removed the UV image on XP2 and the UV pass filter U360 allowed imaging on XP2.
    I am beginning to think the fist image in the thread is the only true UV image.
    see this page
    http://www.naturfotograf.com/spectral.html
    Any ways congratulations on achieving what you wanted, Contratique.
    Regards
    Bill
    "There are a great many things I am in doubt about at the moment, and I should consider myself favoured if you would kindly enlighten me. Signed, Doubtful, off to Canada." (BJP 1914).

    Regards
    Bill

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