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Re: Chroma 50 and 'Plant Bulbs'

On Fri, 22 Jan 1999, Colin Anderson wrote:

> Sorry, but I can't resist.  Why would we use 'plant' light bulbs?  IF 
> LUMENS are in your equation at all...
> You bought the ballast, the fixture, whatever, paid your dues, now GO 
> FOR THE LUMENS!  If anyone would like to refute the arguement that 
> nearly all light grows plants and that more lumens are better, I'd like 
> to hear it :~>


I'm sure you'll get a few of these replies.

The problem is that Lumens is not the same as "usable light" for the
plants. That is more accurately given as PAR.  So if you look at a Gro-Lux
bulb, it's got a very low lumen/watt but grows terrestrial plants better
than a cool white because it has a higher PAR/watt value.  Some research
on PAR/watts was recently done by Pete Mohan (see the URL
http://www.thekrib.com/Plants/Tech/par-moles.html for some initial work,
and the latest issue of _The Aquatic Gardener_ for his excellent (and so
far, exclusive) article).

Also go see http://www.thekrib.com/Plants/Tech/lighting.html#10
for Wright Huntley's ASCII graph of PAR vs. lumen sensitivity curve.
Wright alluded to this in an earlier posting trying to explain this very
subject. :)

My opinion is that it ends up boiling down to a compromize between most
efficient PAR and how nice it will look to the aquarist (CRI and Color
Temp).  Chroma 50's are great because they are cheap, look good, and have
reasonably efficient output.

  - Erik

Erik Olson
erik at thekrib dot com