Posted 11 November 2009 - 05:40 AM
There’s a common misconception that Lumens only refers to white light
This is false, and is usually propaganda spread by LED haters, trying to "disprove" things using basic definitions, hopefully the following clears things up.
All light is measured by Radiant Flux (power) and radiant intensity (the concentration, eg bulb spreads light out, small viewing angle LED concentrates the light intensity)
Lumens refers to the eyeballs sensitivity to the color green, and Luminous Flux is calculated by using the Radiant flux value, multiplied by 1 when the light source is green, and then this multiplier lowers the further you move away from the 555nm wavelength, either up or down the spectrum.
If the light source isn’t exactly green, but made up of different colors, then calculus is used to find the multiplier, it is the integrate of Wavelengths in the bandwidth the Light source is producing.
That means every light that isn’t a green 555nm Led, has had its Lm/w rating calculated by this process, whether its a LED, HID, or a Standard Light bulb.