Re: [Phys-l] refraction question

["John Clement" <clement@hal-pc.org>]

Actually color perception is to a certain extent a low level phenomenon.
The signal from the cones is immediately processed.  When a red cone is
activated it suppresses the activity in the nearby red cones.  The net
effect is that you don't get a signal when from a uniformly colored area.
But you do get a signal at the boundaries going to the brain.  So
essentially the brain gets a cartoon or line drawing where it only knows how
the color changes across boundaries.  So it may well be that many
individuals see slightly different color in each eye.

Because the cone sensitivity is to a broad range of colors it is impossible
to just stimulate a single cone with a primary color.  But because of the
boundary effect it is possible to fool the eye into seeing fairly pure
looking colors.  The same thing happens with intensity.  You only perceive
the difference so something that might be judged white appears gray if you
can put it next to a whiter object.

Of course when I say color is subjective, I don't mean you can change your
mind about it.  It is subjective in that each person perceives something
different, so the color is dependent on the subject and not just on the
spectral composition of the light coming from the object into your eye.
Considering how the information is processed on the way to the brain, it is
a wonder that we can see consistent color at all, but the processing is so
good that the eye is sensitive to many shades and variations of color of
objects in a fairly constant fashion.

Another test of the difference in color between two eyes would be to test
LCD vs conventional phosphor TVs, and different types of colored pictures
such as Kodachrome, Ektachrome, and different types of color prints.  They
all have different "dyes".  Maybe some other people on this list have
noticed this phenomenon.  It may actually be very common.

I just tried it with two pictures on the wall and one eye sees slightly more
red than the other.  The two pictures have different dyes.  It is very
subtle and not apparent with brightly colored objects.  It would seem only
to appear in a picture with subtle differences and muted shades of color,
especially skin tones.  This should not be surprising because evolution has
equipped us with a very sensitive sense of color in the skin tone range.
There is even a theory that color vision arose because we are a social
species.  Color vision helps us perceive what emotions others are
experiencing so it gives us a sense of empathy.  Humans are naturally
empaths, without the need of science fiction, but of course it is not 100%
reliable.  There are other reports on the web of different color perception
in each eye.  One person reported seeing tan in one eye and white in the
other.  Hmmm.

The difference could be due to different densities of cones in the two eyes,
or even having a different dye in the cones.  While this latter possibility
may seem farfetched because the dye is genetically determined it is possible
if you a chimera.  In chimera two fertilized eggs from fraternal twins
joined to form one individual.  This has been proven by genetic testing and
there is even a case of a male/female chimera.  I may even know one because
I know an individual who has different texture skin on the arms with
different hair coloration (not me however).  Again since twins are actually
fairly common chimerism may also be fairly common, but you can't really tell
without genetically testing different parts of the body.  There was a case
where a woman's ovaries were genetically different from other parts of her
body and all of her children tested as being not genetically related to her.

If I remember it I might ask my optometrist about this.

John M. Clement
Houston, TX

> > My eyes each perceive colour
> > slightly differently. This is easiest to notice when I am watching a
> > caucasian newsreader (light skin helps, and they don't move around a
> > lot). The skin tone looks slightly reddish in one eye and slightly
> > greenish in the other. I've tried this many times over the years, and
> > the effect is consistent. So I'm sure that different people see at
> > least *slightly* different colours.
>
> > The effect is subtle, and I doubt most people would notice it unless
> > they went looking for it -- try it out.
>
> Mike
>
> --
> Michael Porter
> Colonel By Secondary School
> Ottawa, Ontario, Canada
> _______________________________________________
>
> I assume that this happens when watching television?  How about in "real"
> life?  Do you see this effect, say, in sunlight with live subjects?
>
> I suspect what you are seeing is a different sensitivity in each eye to
> the RGB colors on the monitor, with your brain "trained" to balance the
> two eyes in normal lighting.