Re: Color

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

----- Original Message -----
From: "Jim Green" <JMGreen@SISNA.COM>
> Class, am I wrong here.  Don't each of us see the "color" of objects
> differently?  EG some see the snow as bluish and others as "white".  I for
> example see purple as reddish and most others as bluish.  This is a
problem
> that artists face in every painting.  At least this is what I have been
> told by eye guys.  But hell's bells what do they know.
How do you know this?  What kind of test have you done to say that you see a
given color as 'reddish' and another person sees the SAME color under
identical lighting conditions as 'bluish'?

I'm not sure what the problem is for artists.  If, for example, you see
everbody's face to have a greenish tint, then if the artist paints a face to
appear the color that he/she sees, it should be accurate even is you see it
as greenish.  Of course your greenish faces are perfectly 'normal' to you.

It seems to me that describing how an individual perceives color is somewhat
akin to describing color to a blind person.  As pointed out, all this
excludes the color-blind where there are obvious problems if two dictinctly
different light frequencies are not destinguishable by a given person.

BTW:  I'm writing a new Optics package for my Animated Chalkboad series and
have something on color.  It is still facinating to me that I can paint the
background of the screen black and then turn every third row of pixels
red--and see red.  I can go back to black and turn every third row of pixels
green--and see green.  But if I paint subsequent rows red then green then
red then green etc. the screen DOES appear yellow.  I can also generate
magenta and cyan screen this way to demonstrate this color addition.  Repeat
the pattern row1=red, row2=green, row3=blue and fill the screen and you do
perceive white.  We all know this works but you don't need an expensive demo
device (or even three flood lights) to see it--just a computer monitor and a
few lines of Basic code.  The demo I like even better though is to generate
a white screen and then project it with a three gun video projector.  Then
stand between the projector and the screen (hold a pointer for a really good
effect) and look at the yellow, cyan, and magenta fringing around the
shadows.

Rick Tarara

**********************************************
Richard W. Tarara
Associate Professor of Physics
Saint Mary's College
Notre Dame, IN 46556
rtarara@saintmarys.edu

FREE PHYSICS INSTRUCTIONAL SOFTWARE
www.saintmarys.edu/~rtarara/
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******************************************************


> BTW red/green color blind people perceive both colors the way most do grey
> -- although I don't know how anyone could tell.
>
> At the extreme I don't know that others don't see the sky as the same
color
> as I do green or yellow -- and they see trees as I do the sky or maybe
> marigolds.  I wonder if it is possible to measure this.  Can someone
please
> comment on this point.
>
>
> Jim Green
> mailto:JMGreen@sisna.com
> http://users.sisna.com/jmgreen