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Re: Watts, Lux, Lumens

>It turns out that plants don't really care that much where the spectra
>are as long as they fall within the range 400 - 700 nM.

Is this really true? As I understand it PAR sensors are calibrated to be
less sensitive to toward the blue end of the spectrum as plants
photosynthesize on a per photon basis. Photons at the at the blue end of the
spectrum contain higher levels of energy but more energy does not translate
into more photosynthesis. Also I wonder why PAR sensors are not less
sensitive to green radiation as most plants are green and obviously reflect
green light.

>Actually, until we get data published on the PAR ratings of various
>fluorescent bulbs, the watt ratings may be more representative of PAR
>than the lumen ratings.

I also wonder if you couldn't simply convert a spectral chart of a
particular fluorescent bulb to a PAR chart by reducing each data point for a
given frequency by the appropriate ammount, more reduction for blue light
less for red light. The area left over under the curve could give a good
idea of the ammount of PAR produced by the bulb.
Anyway, I would like to point out that lumens is very useful for comparing
ballasts as long as you use the same tubes with the same phosphors for
comparison.  Speaking of which, does anybody have any information on Icecap
ballasts? I am looking for information like line current and ballast factor
when the ballast is running 2 vho 48" cool white tubes. I am trying to make
a chart that compares lighting systems that produce adequate lighting for a
90 gallon tank to determine which is the most cost effective over the long
term. I have everything I need but I want to include something on vho
electronic ballasts especially Icecaps which seem to be quite popular.

Wayne Jones