Quote:
Originally Posted by aruzinsky
Not exactly.
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Yes exactly.
You seem to have a misunderstanding of "spectrum". LED's produce single frequencies. Sure you can gang up LED's at say, 5nm intervals but still in physics we would never consider that a spectrum. Instead, it is a series of point frequencies. This is why the graph you provided for the "typical spectrum of a household LED bulb" is incorrect. An accurate graph (or measurement) would be a series of vertical bars with no lines connecting frequency point to frequency point.
Now since PAR is a measurement of fitness (similar to least-squares) of one spectrum to another it is completely inapplicable to LED sources.
Further, I have never recommended "a household fluorescent" for plants -- nor would I. Instead I've specifically recommended 6500 Kelvin bulbs installed at a power density of 1200 Watts per square meter of projection -- the projection surface measured one meter from the source.
With regard to lumens, it is measured by flux of the green portion of the spectrum which plants do not use. So "more lumens" never means anything of use for judging benefit to plants. However, I noticed the term lumens is highly touted in head shops.