Originally Posted by
RickinFl
Just a question about the halogen output:
I know that the LEDs basically emit in the visible range, so all (or most) of the lumens are visible light. My understanding of halogens is that they radiate a lot of energy in the infrared range (heat, not light).
As a previous poster mentioned, lumens are a measure of visible light only. But since I want to confuse you further
here's some interesting info. White LEDs actually emit in the ultra-violet spectrum. This UV light isn't visible to the eye, but it's broadcast in to phosporus powder which glows in a variety of colors. The phosphorus poweders are mixed together to produce what we see as a "white" light. The same thing is done with florescent tubes. In a florescent tube mercury gas is ionized and gives off UV light which hits phosphorus powder to produce the white light we see.
With any incandescent light is produced by heating a metal conductor until it glows. This produces a very nice white light but also produces a LOT of heat (infrared). A big chunk of the power put in to the metal element becomes heat so much of the juice in your battery goes towards heating stuff. That's why an LED is more efficient, a lower percent of its power is turned in to heat, more of it goes towards visible light.
Amid all the hub-bub around lumens the REAL important factor is where all those lumens go. A light that makes a lot of lumens but does a poor job focusing them where you need them is not a good light. The only lumens that count are the ones that end up where you want them. So optics are just as important, perhaps moreso, than raw light output.
I really light this site for a good example of optics performance:
http://eddys.com/page.cfm?PageID=493