[APD] Re: Minimum Light Threshold

["Bill D" <billinet at comcast_net>]

Scott said, in part (with light editing):

"  IF we're going to get this far into it, then we might a well
eschew lux since the variations in lux from bulb are not
covariant with how well they make plants grow. At least
Ivo's work certainly indicates that. Plants can use a wide
range of frequencies and humans are sensitive to a narrow
range, centering around the area of he spectrum that is
least useful for plants. Watts might actually be a better
measure than lux.".

Variations in lux from bulb to bulb would show the differences 
in the amount of light energy that is reaching the plants, and 
it is that energy that is important, not how much energy the bulb 
requires to light up.

As Scott said, PAR would be a better measure.  Or, as Tom said,
"micro moles of photon's (or Einsteins/units of quanta) " would be
best.

When I first started in this hobby incandescent lights were the standard
and people still talked about "watts per gallon."  Years later we are 
still using it, and defending it.  It is long past  time for an upgrade.

Bill
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