Quote Originally Posted by khyberkitsune
You cannot use luminous flux to measure monochromatic light in red or blue. The lumen is weighted at 550-555nm - green.

The only true measure of diode efficiency is radiometric output.

If red were more efficient (and higher electron-voltage) then it would be used as the base for white diodes. As it is, blue is used because of the ease of downconverting from blue light to red light using phosphors. Upconverting requires special tricks like frequency doubling (making a red diode output a 'green' light) and is horribly inefficient, moreso than a normal HID lamp.
I wasnt using it to measure anything. I was wondering why my eye saw the opposite of what the specs stated, a lower brightness.