--Lee Poulsen
Pasadena area, California, USDA Zone 9-10On Jan 23, 2004, at 2:24 PM,
IntarsiaCo@aol.com wrote:

And in a similar vein, from what I've read, humans will perceive two
colors as being the same if they both lie at the same coordinates in
the CIE standard color space, no matter how the color is produced. If a
human sees a source of light consisting of two different frequencies in
the visible light spectrum, it will appear as a single color that lies
at the midpoint between the two frequencies locations in the standard
color space. However, this point can often correspond to a source of
light consisting of a single frequency. Either one of these sources of
light will appear the same color to most humans, even though one is a
spectrally "pure" frequency corresponding to that color and the other
is really two other colors that have mixed to produce that color.

Why is this important? I've read that if you are trying to attract
flies to a bright yellow colored object (like sticky fly traps), you
have to use spectrally pure yellow paper or whatever. If the color of
the object that appears bright yellow to us really consists of two or
more pigments whose mixture appears bright yellow to us, the fly eye is
different and they don't see it as yellow at all. This is also why some
kinds of blue objects appear different colored in photographs than
other blue objects like flowers for example, making blue flowers very
difficult to render correctly to our perception. The photographic
chemicals react differently to spectral reds and spectral blues than
our eyes do making the flower often look wrong, even though to us when
we look at it directly, it looks like it's "pure" blue.

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