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Re: [APD] Optimum Photosynthetically Active Radiation Values forAquatic Plants ? and relation to uW/nm/lm ?

At 04:17 AM 3/20/07 -0700, you wrote:
>PAR involves the what portions of the spectrum are emitted by a lamp.
mesurements like lumens or lux won't differentiate so long as the emissions
are within the spectrum visible to humans.
>Theoretically you could derive PAR for a given bulb if you had a measured
graph of spectral output and lumen measurements. But you will be hard
pressed to find the former for most bulbs.
>The way to get usable PAR measurements would be to measure with a PAR meter
at numerous locations within the aquarium and under the bulb. Measuring
directly below the bulb won't give a good indication of the actual useful
output because such a measurement doesn't take dispersion into account.
>However, any white light will serve well since white light comprises the
full range of visible light (or a balance or red, green, and blue spikes),
which, it happens, includes the PAR regions. And in particular, triphospor
fluourescents and white metal halides work very well.

Here's my take on PAR values for plant lighting.

Fuckit, use a brighter bulb and don't worry about it.

More than enough of the wrong light is better than a bit
of perfect light. The plants utilization of "wrong" light
is still very good. Use whatever bulb is on sale.


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