Re: [APD] Optical Psycho -- and other pathologies of fluorscent lamps

["S. Hieber" <shieber at yahoo_com>]

Welcome Back, Wright. Long time no hear. ;-)

A slightly more detailed explanation was provided some time
ago but, uh, well, it was by Wright Huntley:

http://fins.actwin.com/aquatic-plants/month.200302/msg00240.html

The website Wright listed in that post is a pretty good
website for describing the human sensistivity to green,
too:

http://www.photo.net/photo/edscott/vis00010.htm

Human vision humps just where plants bottom out.

Also, as the color space chart on the page Wright cites in
his older post shows where color temps fall on the CIE
color space map:

http://www.photo.net/photo/edscott/vis00020.htm

A simpler place to start thinking about the CIE chart is
this page:

http://photography.about.com/library/weekly/aa031703b.htm

And when your curiosity is not thereby sated, try this one,
which has a few good comments re fluorescent lamps:

http://www.answers.com/topic/color-temperature

It has some confusing comments regarding lower energy light
being warmer and higher energy being cooler, but this is
following the lingo artists have used for centuries in
dscribing blues as cool colors and reds as warm, which, it
turns out, happens to be the opposite of the energy level
of the photons for those colors.

So use color temp ratings of fluorescent bulbs as a rough
and inaccurate estimatation of how the bulb will look (more
or less bluish). Use the CRI rating as an indication of how
much a fluorescent bulb will make things appear like they
are under incandescent lighting CRI seems like an awful
goal to me, since incandesent bulbs don't all have the very
same spectral outputs (in fact, for a given bulb, it will
vary with voltage!), and they tend to have much too much
red for my tastes).

dimmer every day,
Scott H.


--- Wright Huntley <whuntley at verizon_net> wrote:
> >
> >
> > 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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