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Re: Lumens per liter

On Wed, 6 Dec 2000, Wayne Jones wrote:

> That seems pretty much in line with what I think. If you have very good
> reflectors 200 lumens per gallon will grow anything I have tried but then
> again I havn't tried everything. The problem with a lumens per liter (or
> gallon) rule is that you have to know some hard to get information about
> your system in order to apply the rule.

Well, all those details are far too involved to constitue a "rule of
thumb".  I suspect that the 30-50 lumen per liter rule is based on nominal
lumens -- i.e. on the lumen rating of the light source.  If you need to
base something on actual lumens then probably you're better off getting a
meter, measuring lux and converting to lumens.

Lumens are a measure of light as perceived by the human eye; plants
respond to light in a very different way.  Maybe Ivo can comment on this,
but I seem to remember from comparing across a number of commonly used
fluorescent lights that the wattage rating of a lamp was about as accurate
as it's lumen rating when you need to estimate the light's
photosynthetically active light output.

Roger Miller