Andy:
I have not seen the NatGeo photographs but some time ago I did some
reflected UV and UV excited fluorescence of caique parrots. Used Sunpack
flashes with Wratten 18A filters to restrict output to long wave UV. See:
http://www.davidhazy.org/andpph/exhibit-caiques.html
Best flash units for UV output are older flash units that did not have a
UV absorbing coating over the flash tubes. Wedding photogs in particular
would need to place UV absorbing filters over heads to prevent
fluorescence of wedding gowns causing them to glow blue and this would
introduce color correction nightmares for the labs.
For long wave UV you don't really need quartz lenses. To do reflected UV
photography you can use the Wratten 18A or equivalent over camera lens.
If your converted to IR camera does not have the IR filter built into the
camera then it probably can be used to record long wave UV ... otherwise
a "regular" camera may be useful. B&W film is an alternative for
reflected UV. For UV excited fluorescence a regular camera (color film or
digital) will work.
Unfortunately the Wratten 18A or equivalent is relatively expensive.
a cobalt chloride solution also makes a damned fine UV pass filter, however
the stuff is rather toxic..
Alternatively, UV Fluorescent light bulbs or incadescent bulbs can be
carefully broken and the glass sleeve used to sheathe (or just cover at
least) a flashtube.. or just use them as-is.
Are we smearing the film with Vasoline/mineral oil for this? I'd hate to
think how much the cleaning bill would be if someone did this to a digi
sensor!
k
