I can't get even similar irradiancevalues from a lamp.

Also, I'm curious how you'd use LAMPCOLOR for a UV-lamp? Obviously the
efficacy would not be the usual 179?

Well, it is probably not. But if you multiply the 7.5W to get the lumen
output, lampcolor will internally divide by 179 to calculate back to
radiometric values, so the result should be fine (as long as you do not
start to multiply the results of rtrace to get anything like lux or nits
from what is not visible light :wink: )...

One nice problem if comparing the result to experimental measurements
will be that the lamp's age will probably show some influence on the
real output. So most probably something like 7.5W*0.9 or 0.8 would be
more realistic. But I have NO experience with this UV stuff, so this is
something to find out first.

CU Lars.