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Thread: Lumens and PAR
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post #39 of (permalink) Old 02-18-2003, 12:58 PM Thread Starter
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Join Date: Jul 2002
Location: Winston-Salem, NC
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Hmmm, interesting. More green output than I'd imagined it would have.

Bala, the guidelines you stated for CRI, lumens and color temperature are usually aimed at four foot 40w F40T12 bulbs (the most popular size). There's one I would disagree with. Generally, a high CRI won't have the spectral output a plant desires. The true way to choose a plant bulb is by its PAR, but since that information isn't readily available, indicators you should use are:
1) CRI in the 80-90 range.
2) Color Temperature in the 5000K-6500K range.
3) Slightly less than average lumens output. (Avg 40w tube makes 3000, so 2000 is typical of a plant bulb)

The reason for number 3 is that lux (lumens) is a measure of light intensity, based on a color spectrum that humans are most sensitive to (most sensitive to green). Plants are exactly opposite - they are less responsive to green and more so to red and blue. So a bulb with uncharacteristically high lumens output will likely have a ton of light that we can see, but less light the plants can see.

As Marcel mentioned, all of this information is contained in much improved detail in the article posted in the first post of this thread.

- Sam P -
plantedtanker in limbo - all tanks currently in storage
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