[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: light intensity

George wrote:

If you are *really* serious about proper lighting, you would get a lux meter
(about $100) and stick the probe in your tank and see how much intensity
plant is receiving. And be able to properly convert the measured Lux to
photosynthetically active radiation (PAR) [I think that's what PAR stands
using correction curves (Lux meters are tuned to response of the human eye
which tends to be biased towards green light). And, based on The Table
starting with Allgayer and Teton and added to by APD people), rearrange
your aquascape or modify your lights or pick different plants.

Wouldn't it be cool to be able to say "requires between 1500
and 2000 Lux to grow properly" rather than "Didiplis diandra needs 2.7 w/g
all the assumptions about tank size, bulb quality, reflector shape and
everything else which means nothing to most people]"?

I reply:

I think this is an absolutely capital idea. It is so difficult to predict
how much light is going to actually make it to a plant leaf but very easy to
measure it. I remember an article in the Aquatic Gardener that gave
conversion values for various lamps. I believe the values should be quite
accurate as I think the fellow actually had a PAR meter and a Lux meter. His
conclusions though might be dependant on the particular Lux meter he was

I think that conversion values can also be calculated from spectral
distribution curves without knowing the actual area under the curve. You
could pick a spectrum such as an 840 or a cool white spectrum and compare
all other lamps to that one. You could then say that  Didiplis diandra
requires 1500 CW lux to grow. If you have a different lamp with a more
favourable spectrum that emits more photons per lumen you just have to
divide the 1500 by the factor for that lamp.