[click on image to see a larger one]
Visible light shot:

Simulated bee vision using XBV3 filter :

Simulated bee vision using XBV2 filter:

Simulated bee vision using XBV6 filter:

UV using Baader-U filter:

It only has a quite small focus shift of about 1/2mm when shooting macro, but that could have been expected from a well corrected quartz fluorite lens.

UV transmittance is also quite good, as was expected from a quartz-fluorite lens and stays rather flat even beyond 300nm.
More about that used quartz fluorite lens is HERE.
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