Seeing colors

As told before one can observe colors with the conical cells of the retina. There are three types of cones and each type consists of its own pigment: red, green and blue; the so called primary colors. The range of thousands of different shades which a person can distinguish is all diverted from these colors. The brains take care that one cannot only see the right proportions, but also the right colors through the signals of the cones. That the same color is being experienced differently, is the result of the quality of the light. At lamplight everything has another color than at sunlight.

Someone is color-blind when one isn't able to distinguish colors. The sensitivity of color-blindness is often hereditary and occurs mostly with men (8%) than women (0.4%). Mostly the colors green and red are mixed up. Because the traffic lights are designed according to international agreements, everyone color-blinded knows when the red light is on because the upper rounding lightens up, without recognizing the color as it is.

Sensitive cells

There are three types of sensitive cells, one to all primary colors: blue, green and red. The light stimulates three types of cones in several degrees, depending on the wavelength of the light. The result is a secondary color. The human eye is able to see 160 secondary colors. With the apes we are the only mammals which can detect the three basic colors. Bees, butterflies, fishes, amphibians and some reptiles can see colors too.

If only one kind of cone is stimulated, you only see one color. When all receptors are stimulated you see white. With people who are color-blind, the cones don't work in the way they should.

Seeing images

Each eye transfers its own image to the brains. Because both images are being combined perspective and depth exists. To experience this you can do the following test. Close one eye and try to touch an object which lies on a table about 30-50 centimetres in front of you in only one try through the air. In all probability you won't succeed. When you open both eyes, it won't give you any trouble. This proves that the eyes can only see three-dimensional when they cooperate and therefore and make it possible to estimate distance.

However, if one looks with both eyes the range of view is limited. Only a small part of the range of view will be sharp. What takes place behind it will be picked up but won't be clearly.

Still this part is important as well. When a car appears in the corner of the range of view, one doesn't see it sharply, but good enough to be warned. Thanks to the brains it's possible to see many images without recognizing them. Images at present are being compared to images from the past.

Besides perception also interpretation is very important to the brains. Just take a look at the (tric-) pictures. The brains are mislead by which the things look in a different way than they really are. Take a close look at the horizontal lines in the large image and see if they do parallel each other. And which word can you read in the small frame? (This is the Dutch word for: nice or sweet).