# [thelist] [ot] what is Color Temperature ?

Jason Elliot Burk jasonb at halstead-architects.com
Fri Oct 6 11:13:53 CDT 2000

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> But then, yesterday, I complained to a coworker about some ocasional
> headaches I get after long sessions with my PC.
>
> He suggested, lowering the monitors color temperature. Nor only does
> the image in my monitor look more crisp it is more easy on my eyes.
> I also didnt know that monitors had that setting.

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straight out of my _Mechanical and Electrical Equipment for Buildings_
(MEEB as we call it in the industry) bible, page 961 explains color
temperature:

"A light source is often designated with a color temperature, such as
3400 K for quartz iodine lamps, 4200 K for cool white fluorescent tubes,
and so on.  This nomenclature derives from the fact that when a
light-absorbing body (called a black body) is heated, it will first glow
deep red, the cherry red, then orange until it finally becomes
blue-white hot.  The color of the light radiated is thus related to its
temperature.  Therefore, by developing a black-body color temperature
scale, we can compare the color of a light source to this scale and
assign to it an approximate "color temperature," that is, the
temperature to which a black body must be heated to radiate a light
approximating the color of the source in question."

> Can anyone explain me what Color Temperature is and what difference
> it made when I changed that setting in my monitor ?

I think your co-worker was mixing the wrong terminology with your
phenomenon of headaches, yet the situation i'm sure is felt by many
late-night computer magnets.  However, to give you more perspective, the
CT of a normal incandescent lamp (like a normal bulb) is between 2,500
and 3,000 degrees Kelvin.  Compare that to a standard fluorescent lamp
which corresponds to between 3,000 and 4,500 degrees Kelvin.  Now don't
ask me what that means empirically, but i can tell you that fluorescent
lights -- although more efficient for energy usage -- destroy my eyes
after long periods of time beneath them.  Colors aren't represented as
warmly when viewed beneath fluorescent lamps.  Incandescent bulbs,
however, emit such a warm and comfortable light quality, much like a
sunrise or candle flame -- both of which have CT's under 2000 degrees K.

Although I have never heard of a knob or setting on a monitor that can
adjust CT, perhaps what your co-worker meant that some setting on your
monitor can change the quality of light emitted from it to a warmer,
less harsh and less glaring quality.

in layman's terms, i think you could reduce the wear on you eyes with
the brightness and contrast knob.

take it for what its worth.

jason
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http://www.bsu.edu/World2000/research/burk/
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