[rescue] SGI Challenge L systems available in Denver

John Williams teecee50 at pacbell.net
Wed Sep 29 23:06:35 CDT 2004

    Well, actually, the sun isn't yellow at all.  It has a black body
radiation tempurature of about 5600 Kelvin.  How people
percieve color is affected by all sorts of things.
    The sun is as white as it gets when it is local noon.  At that
time the atmosphere is thinnest between the sun and the observer.
Most folks who manage to look at the sun for any length of time
precisely during or around local noon don't see anything at all
forever after.
    Anytime after local noon the sun is filtered through more and
more atmosphere and is subject to refractive effects.  It appears
to shift from hot painful white to yellow and then orange and
    Anytime the sun is in a position low enough in the sky that
we can tollerate looking at it it appears somewhere in the yellow
to red range.
    It isn't surprising that the people in your study prefered slightly
yellow light and called that "natural".  I assume that this was an
american or western school.  Western cultures have a bias toward
"warm" yellow or redish color ranges.  If you don't believe me
have a look at a color print made with a Kodak negative and printed
on Kodak print paper then have a look at the same thing with a
Fuji-chrome negative and the same companies print paper.
    Oriental cultures have a preference for more blue-green in
their photographs.  Fuji mainly markets in the orient so they
tailor their product to their market.
    Most "Daylight" film is recomened for use between ten in the
morning and two in the afternoon.  At other times the rendering
of color by the flim will start to be noticably "off" to a trained eye,
but then we do all this color correction magic in the printing and
make the end result look like what we expect.
    And that is the point here.  People see what they expect to see,
what they want to see and what they are comfortable seeing.  Your
experiment didn't prove that sunlight is slightly yellow.  It demonstrated
that people prefer slightly yellow light.
    Oh, and if you think 5600K is yellow, try popping a photographic
strobe in your face sometime.  Strobes are made to be used with
daylight balanced film and do a good job of simulating the spectrum
of sun overhead noon type daylight.

....on another note...   anyone have any E6500 parts they want to
donate to a good cause?  :)

John Williams
The Kerckhoff Marine Laboratory
Corona Del Mar

Charles Shannon Hendrix wrote:

> Sun, 26 Sep 2004 @ 16:20 -0400, Phil Stracchino said:
> > On Sun, Sep 26, 2004 at 02:31:40PM -0400, Charles Shannon Hendrix wrote:
> > > I prefer yellow light.
> > >
> > > I wonder if that has something to do with being a human being on a
> > > planet with a yellow sun?  Hmmm....
> >
> > If you get a good blast of straight sunlight while your eyes are
> > night-adapted, it'll look awful blue.  Our sun may technically be
> > yellow, but our sunlight is very blue by the time atmospheric scattering
> > gets done with it.
> I know that... but that doesn't mean that an artificial light of the
> same color will look like sunlight.  Also, sunlight also reflects the
> colors of the local area: vegetation, airborne elements, buildings, etc.
> The overall affect (outside of cities anyway) is definitely not a pure
> white light.  Those look unnatural.
> Also, despite the blue diffusion of atmospheric light, blue tinted
> artificial lights don't look natural either unless the blue tinting is
> _very_ slight.  Darker blue lights are generally very poor, though a lot
> of people think they are cool looking.
> In college we tested various light sources and most test subjects picked
> a light that they called white, but which was actually a very, very
> slightly yellow light.
> Part of the reason is because obtaining purely white light or even very
> bright blue required extreme brightness, which is often excessive for
> the given situation.
> Very bright white lighting was regarded as not looking natural, and
> flourescent was rated pretty low, even lower than obviously yellowish
> incandescents.
> One day at work a rare occurance made things really clear.  A room had
> been emptied, and bright sunlight was shining in a bank of windows in
> winter.
> You could see side-by-side the difference between sunlight and the very
> pure and very bright white flourescents (coated "super white" bulbs, 100
> watts).  It looked like the carpet was two different colors.
> --
> shannon "AT" widomaker.com -- ["And in billows of might swell the Saxons
> before her,-- Unite, oh unite!  Or the billows burst o'er her!" -- Downfall
> of the Gael]
> _______________________________________________
> rescue list - http://www.sunhelp.org/mailman/listinfo/rescue

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