Finally got an infrared filter the other day, and have been experimenting with lighting with it. Outside direct sunlight, exposures are monstrous, which is kind of fun:
 
The second shot is 14 minutes at f/1.8, iso 800! The difference is about 16 stops of light.
I was quite curious to see how normal flashes would perform in infrared though, having read that xenon tubes do produce quite a large amount of IR.
 <-- control shot at iso100, f/11, flashes at 1/128th power.
 <-- the same shot in infrared, bumped all three flashes to full power and still had to open up to f/1.8 at iso3200 to get a readable image.
The flashes are a difference of 7 stops each, 5 1/3 stops at the lens, and 5 stops of ISO... 18 1/3 stops of light is lost to the filter with the xenon tubes, which is a noticeable bit more than the diffuse-daylight example above (that's 1/262144th of the light that gets through without the filter!). Takes a bit too much power to be practical, but perhaps infrared lightpainting with flash is a viable option to experiment with.
Wondering if anybody else here has had experience with infrared and artificial lightsources?
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