On Thu, Feb 4, 2010 at 8:21 PM, M. Adam Davis wrote: > Further, Lumens specifically measures light output *as perceived by > the human eye*. =A0By pulsing the LED at higher than rated current, "the > human eye" may perceive significantly more light than running the LED > at its DC rating. Actually no, it doesn't work like that. If you pulse an LED, the perceived brightness will be the brightness if it was on the whole time multiplied by the duty cycle. There is no magic to pulsing with LEDs. The real point with lumens being based on the eye's response is that the eye is more sensitive to some frequencies than others, hence if your light source has more power at that frequency it will have more lumens than if the frequencies are equally spread. A pure 555nm green source can be as much as 683lm/W, whilst an ideal white light source is only 251lm/W. Anyway, back to the original LED - 1500lm is good, but as mentioned that's a spread out multi-emitter. Looking at other Cree products, you can get as much as 800lm for a concentrated quad die, or 300lm for a single die, either of which you can focus into a tight beam. -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist