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post #31 of (permalink) Old 11-23-2011, 10:35 PM
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Join Date: Dec 2005
Location: Sacramento, CA
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1000 lumens produce 1000 lux at one meter distance. Multiply lux by .014 to get approximate PAR for cool white fluorescent light (close enough to LED light). So, that 1000 lumen LED bulb should produce 14 micromols of PAR at one meter distance, but that is assuming the bulb emits light through a full spherical angle around the bulb. It doesn't. The light is concentrated into about a 60 degree cone, which is about 1/36 of a full sphere (I think). Therefore the PAR should be about 36 times higher or 36 x 14 = 500 micromols of PAR at a one meter distance. If all of that is calculated correctly, you should get an awful lot of light from one bulb. (At 20 inches, it would be 4X 500!)

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