Today about mold on a gourd and making that visible using reflected UV photography using my "work horse" UV filter, the Baader-U filter. Lens used was an older enlarger lens. Light source was a modified for UV high power Xenon flash.
Here now some results: [click on image to see a larger one]
visible light image using UV/IR cut filter:
UV image using Baader-U filter (approx. 320-395nm, effective peak approx. 375nm):
Differential image VIS - UV:
Well, as one can see, UV and visible image contribute differently to that mold, UV bounces off right from teh surface, while visible light penetrates a bit deeper, which the differential image makes quite visible.
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