Oh, and strictly speaking, what we perceive as, say, "bluish," doesn't
completely result from a relative reflection of short-wavelengths and
absorption of the longer. Do some color-constancy reading, and things
get much more complicated. I can see a pair of jeans as blue when they
are reflecting wavelengths that in other circumstances would make
something appear quite reddish.
Color perception -- even the perception of "black" -- depends on the
illuminant, the reflectance spectrum (or conversely, the absorption
spectrum) of the surface, and the absorption spectra of *other nearby
surfaces*.
m
PS The constancies are *fun* to demo for your classes. You can change
the character of the illuminant in a classroom usually pretty easily: go
from overhead flourescents to the light from a transparency projector to
daylight from the windows. All are different and thus the light
reflected from surfaces in the room will have to change, and yet the
colors of the objects in the room won't -- as long as the illuminant is
relatively broadband. Narrowband lights, like LASERs, screw up color
constancy. You can also mess with it if you can get a different light
to shine on only a small region of a scene that is illuminated by a
different light -- but that's harder to do in a classroom.
-------
"Mauchly's Test of Sphericity:
Tests the null hypothesis that the error covariance matrix of the
orthonormalized transformed dependent variables is proportional
to an identity matrix."
---
SPSS
________________________________
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Tuesday, February 06, 2007 7:12 PM
To: Teaching in the Psychological Sciences (TIPS)
Subject: [tips] question about color perception
Sorry for the cross-posting.
After I explained that when we see a color, that color is what
is reflected after the other wavelengths are absorbed by the material,
one of my students asked about the perception of black. She wanted to
know if it is similar to the black pupil in the eye, which is actually a
hole. If it is the absorption of all wavelengths, how is it possible to
have many shades of black? I told her I would seek the expertise of my
colleagues.
Riki Koenigsberg
[EMAIL PROTECTED]
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