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Re: [Phys-l] images in eye


--- John Clement <clement@hal-pc.org> wrote:

Incidentally there are 2 different possible
inherited color filters
for blue so others may not see color the same way if they
have the other
filter.

The situation is way worse than that. The Exploratorium has
a really cool exhibit that demonstrates (nay, proves) that
the colors you see are not the same as the colors that
other people see.

Here's how the exhibit
<http://www.exploratorium.edu/xref/exhibits/disagreeing_about_color.html>
works:

In the center is a yellow colored dot. Around the center
dot is a circle of colored dots starting with green on the
left and progressing through shades until it reaches red on
the right.

The object is to identify which dot on the outside circle
is the same color as the dot in the center. For most
people, it is easy to select which two dots match. When you
are by yourself, this hardly seems remarkable.

When you are with a large group, though, something strange
happens: other people have selected a different dot as the
match. Further, they are as convinced that they are right
as you are. I was with a group of 20 people that only had
one color blind person (me), and among that group five
different dots were selected.

We just stood there wondering about the crazies around us.
They must be bonkers to select a different dot.

How does this work? The center dot is made by an
incandescent bulb and is a black body yellow. Each
individual dot in the circle is combination of red and
green LED light in different proportions.

So while it is true that yellow light can be simulated with
red and green, it is not the same red and green for each
person.

And this shows up in class. Since I am color blind, I need
help balancing my projectors so that their combined light
will mix to white. However, when I've balanced it right to
satisfy the art teacher from downstairs, it looks a touch
pinkish to the chemistry teacher next door and bluish to
the English teacher from around the corner.

Thankfully, humans have color constancy
<http://en.wikipedia.org/wiki/Color_constancy>, so this
isn't usually a problem.

Marc "Zeke" Kossover