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[APD] Optical Psycho

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.

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


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