[APD] Optical Psycho

[Wright Huntley <whuntley at verizon_net>]

> Where's that psycho-optics fella when we need him?

He's here, and driven around the bend by some of the misinformation in 
this thread. :-) The terrible thought is that some of it gets passed on 
as gospel.

Color temperature is a psycho-physical measurement that says how the 
light "looks" to a "standard observer." The International Committee on 
Illumination (ICI in English and CIE in French) tested a large number of 
individuals and found averages as to how certain nominally white colors 
appeared when compared to blackbodies at various temperatures. The scale 
actually ends at around 10K and higher numbers are just marketers trying 
to foist off non-white tubes (usually very blue).

A 10K with high CRI can look very white. If CRI is down around 80 or 
below, it will be blue.

Basically Color Temp. tells you little about the spectrum or usefulness 
in unintended applications. It was a standard to get store show windows 
to look right, and (sometimes) to make meat look fresher in the display 
case.

Applications to aquarium illumination are a true stretching of the 
original intent.

A true spectral energy distribution plot would be far, far more useful, 
both for predicting photosynthesis efficiency and apparent color 
fidelity and intensity to your eye. Those are what we want.

In LFS lamps, Color Temp. holds about the same place as Megapixels in 
cameras. That is, a great marketing hook, but with little real value to 
the customer.

Wright
Your friendly Optical Psycho

--
Wright Huntley - Rt. 001 Box K36, Bishop CA 93514 - whuntley at verizon_net
                     760 872-3995

"I cannot undertake to lay my finger on that article of the Constitution which granted a right to Congress of expending, on objects of benevolence, the money of their constituents...." --James Madison

              http://www.libertarianism.com/

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