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0. Visible reference, 5600 Kelvin LED
1: Long wave UV lamp w. filtered mercury 2x 4 Watts lights ("blacklights"), 400-700nm dichroic cut filter on camera
2: Cree 385nm UV LED, 3 Watts, 400-700nm dichroic cut filter on camera (this LED leaks quite some blue light)
3: Cree 385nm UV LED, 3 Watts, filtered using 1.25" BaaderU-Filter , 400-700nm dichroic cut filter on camera
4: Nichia 385nm UV LED, 400-700nm dichroic cut filter on camera
5: Nichia 365nm UV LED, 400-700nm dichroic cut filter on camera
6: Nichia 365nm UV LED filtered using 1.25" BaaderU-Filter, 400-700nm dichroic cut filter on camera
7: High Power UV flash, filtered using Schott UG1, 400-700nm dichroic cut filter on camera
8: High Power UV flash, filtered using Schott UG1, Baader UV/IR cut filter on camera
9: High Power UV flash, filtered using Schott UG1, Schott BG38 + 400-700nm dichroic cut filter on camera
10: High Power UV flash, filtered using Schott UG1, 400-650nm dichroic cut filter on camera
Exposure times were between 15s (UV fluorescent lamp), 3-15s (UV LEDs) and 1/160s (Xenon flash), all shot using ISO400 and f11.
I did not try and make "the pattern" visible. The underlying assumption that the pattern using reflected UV and UV stimulated visible fluorescence should not be confused, since it is two completely different mechanisms and it might be just coincidential that both appear at the same time. It would be interesting to study that though, if these both are directly linked to each other (i.e. if the reflected UV pattern and the fluorescence pattern appear simultaneously and if so, why).
You may have noticed, that I tried to cut off the visible part of the exciting light source from about 395nm onwards using a 1.25" Baader U-filter in some of the tests. I wanted to see if that "leakage" of visble light (some blue usually) in the exciting light has an impact on the result - and quite obviously it has, with the exception of the Nichia 365nm UV LED, since that one has hardly any visible content. But still it makes a little, but noticeable difference.
The Xenon light source provides a continuous emission spectrum and using a UG1 like filter, I took out the UV part as exciting light. Now the question is, if the strong visible red in the results is a result of stimulated red+NIR fluorescence, or if it is caused by NIR leakage of the UG1 filter (i.e. reflected NIR). This is why I used three different filters (BG38, Baader UV/IR cut and 400-650nm cut) to see the effect of them.
Here now the proof that IT IS indeed red/NIR leakage:
11: High Power UV flash, filtered using Schott UG1, 400-700nm dichroic cut filter on camera
12: High Power UV flash, filtered using Schott UG1 + UV passing IR blocking filter, 400-700nm dichroic cut filter on camera
Stay tuned, more will follow on that fascinating subject...
More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos
