UV Flourescence of flowers

Discussion in 'Botany Photo of the Day Submissions' started by erniew, Oct 2, 2007.

  1. erniew

    erniew Member

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    I think that I should qualify this post in that the pictures that I'm posting aren't verified as UV flourescence. They follow the patterns of UVF but I've not had them independantly verified. If there is someone here that could, one way or the other, it'd be appreciated. OK.....While fooling around in Photoshop one night, I found something rather interesting. Some flowers exhibit interesting patterns when converted to black and white in a specific fashion. A little research led me to http://www.naturfotograf.com/UV_flowers_list.html It seems that pollinators use the UV spectrum in their hunt for flowers.

    Regards,
    Ernie
     

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  2. newsflash66

    newsflash66 Member

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    Those pictures are really cool. If you wouldn't mind sharing the technique you used to make them I would be interested.

    I have never heard of flowers that fluoresce, but if I had to hazard a guess I'd say that this is not flourescence but a neat photoshop trick. If UV (or other) radiation causes fluorescence, that means it causes the object to emit light in the visible range, so I wouldn't think you'd need to change the photo to B&W to see it, although it may enhance it. Also it appears to me that other parts of the picture, not just the flowers, exhibit the same glow.
     
  3. erniew

    erniew Member

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    Hi newsflash,

    this is easily done if one has a bit of familiarity with photoshop. Open the image, select: image>adjustments>channel mixer>select monochrome>drag blue slider to left for desired effect. I was fiddling with it some more and it seems to effect oranges the most, orange daylilies stayed bright. There were a couple of exceptions with reproductive parts of Oenothera and Photinia. They were a greenish yellow and went to the glowing color. I suspect that this is the real flourescence. Compare these pictures for a real view of how flourescence can not be apparent to the naked eye: http://www.naturfotograf.com/UV_ANGE_SYL.html I'm assuming that Bjorn is correct in his assessment with what he captured. I've attached a picture of Oenothera that seems similar. Digital cameras can capture UV light outside of the visible spectrum although the manufacturers usually put a filter on the sensor so that it doesn't play havoc in the color conversion process. One camera manufacturer ran into problems when they didn't put one on not too long ago. Leica, if I remember correctly. I'm guessing that the cameras that I'm using can capture a limited spectrum of it and it's not apparent till I discard the color information. 'd be interested in your thoughts about this.

    Regards,
    Ernie
     

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  4. newsflash66

    newsflash66 Member

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    This sounds plausible to me. I've a bit of research to do in order to unravel this. I guess I'm not suprised that the flowers fluoresce under a black light (doesn't everything!). What conditions did you shoot the pictures in? Daylight, Artificial light? If the source of UV is small, like sunlight, then I can see where a small amount of light emitted would be overwhelmed by the sunlight itself. There must be a test for fluorescence - maybe see what happens in complete darkness + a black light??

    Another topic for research - do pollonators use fluorescence to find flowers? If this is true I would think a significant amount of the light emitted would have to be outside the visible range. If it's in the visible range, in daytime it wouldn't appear much brighter then anything else. If it's at night, then there's not a significant source of UV - we all know flowers don't glow in the dark. So my hyposthesis would be that insects must detect something outside the visible range. Does a digital camera capture wavelengths outside the visible range and would photoshop allow you to isolate them??

    BTW - tried the photoshop trick. Although I got some neat color variations of my picture I couldn't replicate your method. My version of photoshop must be different then your b/c I didn't have the same menu and couldn't find anyway to make the picture monochrome. I did locate a place to manipulate RGB colors independently.
     
  5. erniew

    erniew Member

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    Hi newsflash,

    I took the pictures during daylight, no flash involved since my camera doesn't have a flash. I suspect that you know a bit more about this than me. I'm looking forward to what you figure out. In the original link to Bjorn's site, he mentions pollinator's using light outside of our visible spectrum. I followed another link to this: http://www.sciencedaily.com/releases/2001/11/011120044731.htm
    As far as digital cameras and their spectral response, it appears that they can capture somewhat signicant amounts of light from around 300nm up to 400nm. At 400nm it really picks up and they can capture light up to 1000nm. I think that the "hot mirror" cuts out light from the upper end but not the lower end. I also don't know how much of the upper end of the spectrum is filtered. Since a Bayer-array camera like mine (Canon) captures images in grayscale and records luminosity, is it possible that it is recording some IR or UV that is masked by the color filters that provide the color information for the image? Converting back to BNW or discarding color information might reveal some of the IR or UV luminosity that had been hidden by the color information. I should post this over at DPReview to see what they'd say. I'm using Photoshop CS (8.0) and the monochrome selection is a little box to check in the channel mixer dialog box that pops up.

    Here are some links about digicams: http://www.kodak.com/ezpres/busines...upportdocs/ColorCorrectionforImageSensors.pdf

    http://www.fis.unipr.it/~fermi/PagInternet_English/Digital_Cameras/DigCam_Choice.html

    Regards,
    Ernie
     
    Last edited: Oct 31, 2007

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