Generally one can consider glass to be opaque to UV, but of course there is some at the blue end of the spectrum. Quartz lenses are needed for real UV filming. I think, in terms of the current problem, that an IR filter (on a camera) will never get hot enough to radiate in the near-infra-red.

Bob, yes colour temperature does assume black body radiation (ie continuous frequencies). The efficiency of radiation depends on the surface (eg. non-black) but if it is just hot (rather than a plasma or other discontinuous source) the colour of the light radiated is related to its temperature. Sources such as cheap white LEDs can be difficult to WB, but the EX surprised me with its good rendition using one of those camping lights. That link above to "peak radiant wavelength" shows the variation of wavelength with temperature, CT referring to the maximum of the curve.

Michael, the red cut is to be expected (with your filter on) because that's where the IR is recorded. Based on the astrophotography example, I wouldn't be surprised by shifts in other colours as well. However you would hope that the red you see and the red reproduced would be close. Unless Sony's default matrix has a cut in red to compensate for IR.

EDIT: just how much IR is in our incandescent light sources is made clear when you draw a 750nM ordinate on http://en.wikipedia.org/wiki/Image:Wiens_law.svghow much IR[/link]; everything to the right of that should be blocked if the recorded image is to match our visual appreciation. 2800K sources (domestic) peak at 1035 nM.

Michael, how has the filter worked out in improving your desert shots?