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Lumen ratings, coverage area

Posted by wordwiz (My Page) on
Sat, Nov 8, 08 at 19:35

Does anyone know - bulbs are usually rated in lumens, such as 4,000 or 6,900 lumens. Is this basically the same thing as lux? I know lux is the amount of lumens per square meter (10.76 sq. feet IIRC) so does a rating of 4,000 lumens mean that the light if placed at a specific distance, one that would cover those 10+ sq. ft., that the lux reading would be 4,000?

Any links to data that explains this?


Follow-Up Postings:

RE: Lumen ratings, coverage area

In another forum a member said he had read that the lumens quoted on bulbs are the amount reaching a surface from one foot away, or in other words, a ft. candle. To get it's lux rating, one would divide by 10.54 (I think that's the amount).

My light meter seems to agree. Taking the reading from about five inches away, I get ~14,500 lux. At exactly six inches, ideally I should get a reading of 13,800, at about two feet I get ~3,000.

IME, 3,000 lumens hitting the leaves of the plant should be enough for seedlings though not enough to set and produce fruit for most plants.


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