VISION OF COLORS

Process of vision of the colors

The human eye and the retina

   The human eye is constituted by three layers, being the most internal of them retina.

The retina presents about 140 million nervous cells that are sensible the light. These cells are formed by the cones and rods. The cones are sensible the light most intense, in turn the rods function in weakker illumination. When in contact with the light these receiving cells generate nervous impulses being transmitted for other neurons, whose the staple fibres that are congregated, form the optic nerve. It is this nerve that has the function to take visual information to the areas of the brain.

   The region of the retina for where the optic nerve leaves does not possess light sinks: being this called place " blind point ", therefore in it the vision if becomes impossible. However it has one another area of the fórvea called retina, or yellow spot, that is highly sensible the light, for presenting grnade amount of cones.

The rods and the vision in environments little illuminated.

The rods only are stimulated, when the illumination is of low intensity. These cells only allow the vision in gray tone. The colors alone can be perceived by the cones.

   In the rods visual púrpura, or rodopsina has the presence of a called substance. How much bigger the amount of same better the our vision will be under weak light. The visual púrpura if drift of the vitamin. It is therefore that its lack can cause to a called illness nocturnal blindness.

The cones and the vision in illuminated environments

When the light is more intense the vision is carried through by the cones, that perceive the details and the colors of objects. The fórvea, for presenting great number of cones, is the region of better visual perception.

The colors of objects

The man has the capacity of enxergar the colors, being differentiated of other animals, that in turn do not possess this " privilege ". But why ratio an object illuminated with white light can appear for example, red?

The objects generally present different properties of reflection. Some when receiving a white light, reflect only the light red and absorb all the others.

In the same way, yellow bodies are those that they only reflect yellow and they absorb the other colors as: red, blue and etc...

Already the black bodies are those that absorb all the colors and they do not absorb none.

OBS: consequent of the absorption of all the colors, the black color is the light absence.

A great majority of objects mixta apresetam color, reflecting a little of each color. In contrast of the white color that reflects all the colors.

PROBELMS WIHT VISION OF COLORS

Color Blindness

Color blindness is an inaccurate term for a lack of perceptual sensitivity to certain colors. Absolute color blindness is almost unknow. There are three types of color receptors in our eyes, red, green and blue. We also have black and white receptors. They are more sensitive than the color receptors, that is why we have poor color perception in the dark.

Color blindness comes as a result of a lack of one or more of the types of color receptors. Most color perception defects are for red or green or both. About 10% of males have a color perception defect, but this is rare in females. Red-green color blindness is a result of a lack of red receptors.

Another form of color blindness -- yellow-blue is the second most common form, but it's extremely rare. It is also possible to have the color receptors missing entirely, which would result in black and white vision.