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watts vs. lumens
>Date: Sun, 14 Mar 1999 07:39:00 -0500
>From: krandall at world_std.com
>Subject: watts vs. lumens
>Bob Dixon wrote:
>>But with the high variablity in lumens per watt these days, that still
>>really tell us anything. I've tried to start a thread that deals
>>with this particular issue, but the responses I have gotten have been
>>best. Can somebody define this rule-of-thumb in lumens per gallon or per
>>sqquare foot? Yes, PAR would be eeven more effective still, but that is
>>to detirmine based on the available info for the different types of bulbs.
Sorry, I donīt know the expression PAR
>But that's the problem. Lumens are NOT a better measure than watts.
Guess it is. Watt is only a measure of the energy put into the bulb/tube and
its ballast ect.
In no way a measure of what comes out. And the output may vary as much as 3
times, depending on
size, type and temperature
Lumens is a measure of what comes out as light ( candela/steradian) and thus
better, but far
from good enough
>measure only the visible part of the spectrum, which is the part of the
>spectrum least used by plants.
Are you sure this is correct. As far as I know plants use
ultraviolet-violet(visible)- blue(visible)-a little
But maybe Iīm not up to date on this ?
A lamp with good output in the areas of the
>spectrum used best by plants can have a low lumen rating, and still grow
>plants well. (Like purple-ish Gro-lux, etc.)
These, like Gro-lux, are not considered well suited for aquarium use any
more in Europe ( Kasselmannn and others)
A lamp taht expendes most of
>its energy in the visible range will have less of the wave lengths that
>palnts use more efficintly, even though they look "brighter" to us.
>Whether we like it or not, without PAR ratings on a lamp, watts plus a
>spectral chart are still as good as we're going to get for now when
>guessing how a particular lamp might perform.
>(and those high lumen output lamps will also work adequately if you use
>enough of them)
ole.t at larsen_dk