Easter is approaching and quite some shops exhibit the traditional easter decoration. I was curious to see, how that white ostrich egg would look multispectral.
[as usual, a click on an image opens up a larger view]
Now that made me curious and the idea was to investigate the behaviour in terms of fluorescence these eggs (their eggshell more precisely) might show.
A Baader 2" UV/IR Cut Filter was used for the visible and fluorescence light shots, a Baader 2" U-filter for the UV shots together with that calibrated X35 lens I made, the UV Nikkor 105mm and an unmodified Nikon D70.
Now the big surprise is, that brown eggs exhibit some very unusual behaviour - they glow mysteriously red if you point a UVA light source to them; in that case here I used my mobile UV LED flash/lamp.
So why is that you might ask. It is UV stimulated visible red fluorescence of the porphyrine contained in the brown eggshells! This can be proven using a spectrophotometer (USB2000 in my case) which measures the reflected and emitted light from that eggshell with a fiber optic probe. The excitation source is quite strong, this is why that 365nm line is way off that graph. You see some response around 480nm (blueish) plus these two red porphyrine peaks at 675nm and a bit weaker 635nm.
Remember the first white ostrich egg shot I showed you above? I wondered if that one would also exhibit that effect, but the visual experience and the spectrophotometer reveals only a strong blueish response around 480nm plus a quite weak peak at around 635nm.
That made me even more curious and I got a fresh set of eggs from another vendor and indeed there it was again, that red fluorescence. Quite weaker but it was there, aside of some strong blueish fluorescence (as with that white ostrich egg):
The spectrometer confirmed these visual findings, the porphyrine response is clearly visible:
So I hope you enjoyed today this more scientific journey with me!
Stay tuned, more will follow on these fascinating subjects...
More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos
Friday, February 29, 2008
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