(See yesterday’s entry also). Using an unmodified Nikon D3 and a two-filter stack (Tiffen Hot Mirror over a B+W 403 Ultraviolet UV black), there does seem to be some response from the Nikon D3, though it might well be something besides UV and/or in addition to UV. Results with the Baader “Venus” filter (original version) are similar (and about two stops faster). The word from UV guru Bjørn Rørslett of naturfotograf.com is that the results are likely due in good part to infrared that has not been adequately suppressed.
And whatever it is, the color variation might be due to the filter stack rather than inherent in the scene. Whatever the spectral band, it’s eye-catching at least.
Nikon D3 + Coastal Optics 60mm f/4 UV-VIS-IR APO macro
(15 seconds @ f/5.6, ISO 1600)