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Re: PAR, Lumens, Watts, etc
On Wed, 17 Mar 1999, Michael Dubinovsky wrote:
> Here is data from "Proceedings International Lighting in Controlled
> Environmets Workshop" 1994. Gerald Deitzer - "Spectral comparison of
> sunlight and different lamps"
Great info, Mike. Thanks.
> Table 2 provides amount of energy in W/m^2 relative to number of photons of
> PAR (400-700 nm) for each lamp. ALso, it allows to calculate illumination
> level if you know PAR (mk mol /(m^2*s)).
> PAR/(W/m^2 per mkmol/(m^2*s)) Lux per PAR (mkmol/(m^2*s))
> Sunlight 0.22 55.18
> Incandescent+1/8" plex 0.20 49.00
> Cool WHite + 1/8" plex 0.22 78.75
> Vita-Lite 0.22 62.78
> Gro-Lux original 0.22 37.02
> Gro-Lux 0.21 55.09
> (wide spectrum)+1/8" plex
> Microwave+1/4" plex 0.22 67.43
> 100W Incandes. 0.21 74.53
> (1:3 ratio) + 1/8" plex
> So.......cheap Gro-Lux is the same as expensive Vita-Lite (even better in
> blue and red regions). And combination of CW+incandescent is good also (you
> can find similar data in Philips Lighting Handbook)
Well, maybe not. It looks to me like the column on the left shows that at
the same PAR, the vitalite will appear much brighter than the gro-lux
(higher Lux/PAR - Lux is lumens/square meter). In fact CW+incandescent
would be about twice as bright as the gro-lux, and CW alone would be more
than twice as bright, even though they're all producing the same PAR.
This is another illustration that lumens (or lux) are a poor measure for
judging the quality of light for growing plants.