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Re: [APD] Re: Luxed out -- or - Lax on luxing

I think I said it right.

As for European, I meant metric's a European thing -- we
use feet and inches here in the backwards New World.

You can go back and forth between Footcandles and Lux via:

Lux to Fc:

Fc = Lux x .0929

Fc to Lux:

Lux = Fc x 10.76

--- Wright Huntley <whuntley at verizon_net> wrote:
> Join the crowd. Even our usually-accurate Scott got this
> one messed up. 
> :-) Lux is a standard photometric unit that isn't just a
> "European 
> thing." As I recall it's the metric equivalent of the
> foot-Lambert, and 
> describes how well a surface is illuminated. It is a
> lousy choice for 
> lamp rating, BTW. Lumens is better, IMHO.

Yes, the amount of light falling on a square meter of 
surface -- I said planar and I think that was a mistake --
it';s jsut one meter form the light source.  A footcandle
measures light one foot away from the point source. 
Sometimes, the measurers don't bother with the distinction.

> It is, but that's per *square* meter. Doesn't mean much
> for plants, and 
> often is very misleading. Converting from lumens of
> apparent brightness 
> to a surface measurement requires definition of the
> measurement 
> apparatus. Yes, longer tubes will generally be able to
> deposit higher lux.

As for colors. you can raise the color temp rating of a
bulb by filtering out light at the lower end of the
spectrum and you can raise it by filtering out light at the
upper end.  So two similar bulbs but one with a higher
color temp is necessarily yielding more or less light --
could be either.

Color temp doesn't even tell you the color ofhte light from
the bulb -- only a graph of the outputs by color can
tellyou that.  Color temp is like an average of tjhe
intensitiis of all the colors the bulb gives out.  A narrow
big spike at the high end can move the average up and one
at the bottom can move it down.  The best that can be said
for color temp is that high ones tend to be bluer and low
ones tend to be yellower or redder.

Scott H.

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