Difference between revisions of "Light Output Measurements"

Light Output Measurements (view source)

153 bytes added , 22:24, 19 February 2011

add lumens for 40-watt and 60-watt lightbulbs as a comparison

confirmed, developer

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 ==Lumens==
-Lumens are a measure of the total light emitted by a LED or flashlight (see [http://en.wikipedia.org/wiki/Lumen_%28unit%29 Wikipedia article] for more information on lumens). Lumens are sometimes measured "at the emitter" or "out the front." Emitter lumens will always be higher than out the front lumens because there are some losses involved as the light bounces off the reflector and is filtered somewhat by the flashlight lens.
+Lumens are a measure of the total light emitted by a LED or flashlight (see [http://en.wikipedia.org/wiki/Lumen_%28unit%29 Wikipedia article] for more information on lumens). For scale, a 60-watt incandescent lightbulb produces 890 lumens, a 40-watt bulb is 460 lumens, and a pretty decent flashlight produces about 200 lumens. Lumens are sometimes measured "at the emitter" or "out the front." Emitter lumens will always be higher than out the front lumens because there are some losses involved as the light bounces off the reflector and is filtered somewhat by the flashlight lens.
 '''Emitter lumens''' LED manufacturers publish specifications listing the lumen output of their LED's (see [[Brightness Bins]]) and sometimes flashlight manufacturers will just take the highest value for the LED in their flashlight and say that is the output. But actual output depends on the voltage and current delivered to the LED. Even then, these numbers are always going to be higher than the actual light output by the flashlight.