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Re: [APD] Re: Ideal Lights
At 08:27 AM 3/3/2005 -0500, you wrote:
>"Intensity matters, spectum is neat irrelevant in my experience. Grolux
>supplies lots of red that plants need. Look up at the sun, does that look
>blue to you? :-)
I'm referring to the current fashion statement of "the more K the
better" in fluorsecent tubes. 5000K, 6500K, 7500K, 10,000K, 18,000K
it goes on and on. Somewhere near 5000K is perceived at "white"
and the higher the K number the more blue it should be; never mind
that some of these high K bulbs look pink (how does THAT work?!?)
Horst and Kipper measured the color temperature of light in the tropics
and of course it matches no fluorescent tube because it isn't constant.
Their measurements ggo from 3500K to 6500K t noon back down to 3500K.
So, the next time you get a bluish tube, look up at the sun, that
big *yellow* ball in the sky. How blue does it look?
I spent a couple of days looking at the "what's the best color
to use for plants" question by reading everything that's been
written on the net in the past 20 years. Here's the relevant
points I found, and I have no idea how true or applicable they
o Algae do better with blue light
o Plants need more red than blue
o Philips tested all bulbs and found 10% difference
between "best" and "worst".
o Tropica uses sunlight, shaded, and adds (Yellow!) HPS
in winter to augment Danish northern daylight (northern
latitudes have a more bluish color as a result of scattering
of light which reflects the blue end of the specrtum)
What I found in my experience is whether I use warm white,
cool, white, grolux, 6500K, 7500K, vita-lite, it doesn't seem
to matter much if at all. In fact the only thing I've ever doe
that gave me any sort of dramatic difference was when I stuck
a fixture on a 25L that was a surplus light. The reflector,
which was once very very nice is now brown with age, the (warm
white!) tubes are very very old. But, it's 2 X 40W compact
fluorescent tubes. And plants explode in this tank. So, even
with tubes everybody knows are useless (warm white) you get enough
intensity from them and you'll do better IMO than if you use
lower wattage tubes, even though they may be $40 Tritons.
That's why I say intensity matters, spectrum doesn't.
Horst and Kipper recommmend 5000K tubes FWIW.
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