How do our eyes recognize light

See color

No color without light

Without light there would be no color in the world. If you let white light fall through a glass prism, you can see that the light breaks in the glass body and splits into different colors.

Because light consists of electromagnetic waves, each color has a different wavelength and is curved to different degrees in the prism.

That means: White light is composed of colored lights, the so-called spectral colors. You can also see it in a rainbow.

The English naturalist and mathematician Isaac Newton (1643 to 1727) discovered the different colors of light, including the three primary colors red, green and blue.

Incidentally, we only see around 40 percent of the colors in sunlight.

Additive and subtractive color mixtures

A basic distinction is made between so-called light colors and body colors.

The light colors appear in the light spectrum, while the body colors go back to the properties of material bodies, for example grass.

That is why there are two types of color mixing. One is called additive color mixing - it is created by adding two or more colored light sources.

An example: if you mix red and green light, the result is yellow at the interface where the two light colors mix.

If you then add violet-blue light, cyan-blue and magenta-red appear at the other interfaces. In the middle, where all three light colors overlap, white light is created.

In the case of additive color mixing, the radiant energy of the colors is added, which means: when the light colors are superimposed, lighter shades are created.

Of subtractive color mixing one speaks against it when radiant energy is removed from a light source by filtering or absorbing it. This is exactly what happens with the body colors.

When they mix, the individual body colors act like filters and absorb certain parts of the light.

The result: the more body colors mix, the darker the result of the mix, because light is withdrawn with each new body color.

Here is an example: If you slide blue and yellow in front of a white light source, green is created.

The colors of the objects

The objects in our world get their color by swallowing different rays and reflecting others, depending on the material.

For example, water absorbs long-wave light much better than short-wave light. The red component of the sunlight is therefore already swallowed after a few meters under water.

If it goes even deeper, the orange, yellow and green parts disappear one after the other. The blue light, on the other hand, is absorbed the least and is reflected the most, i.e. it is reflected back to the surface. That's why our seas are blue.

The lush color spectrum of nature is nothing more than differently absorbed and reflected components of our sunlight.

When we see color, we are basically seeing colored light that has previously taken the detour over the surface of an object.

Color vision in the eye

The color vision of our eyes is based on the principle of mixing colors. It has a similar structure to a digital camera.

The incident light is focused by the lens and is focused on the retina. The iris regulates the amount of light depending on the brightness like an aperture.

The retina has sensors that are sensitized to different light. They divide into two types of receptors that receive light.

Using a chemical reaction, they generate impulses that are passed on to the color center of the brain.

Brightness and color

One type of receptor is called rods: They react in roughly the same way to all colors and thus capture uncolored impressions of brightness. If we only saw with them, the world would appear black and white to us.

The other type of receptor is responsible for our color vision. They are called cones. There are three different types of these that are sensitive to different color ranges, red, blue and green.

The three color areas and the corresponding brightness impressions are then brought together in the brain - we see colorfully.

As long as it is bright day, cones and chopsticks work together. With decreasing light and the onset of twilight, the rods take over the vision

In the dark of night only the rods are active.

Color defects

Color ametropia occurs when a type of cone is defective. For example, the red-green weakness is known, in which the affected people cannot distinguish between red and green.

This can lead to difficulties not only in traffic with traffic lights. When all types of cones are defective, it is called color blindness. Statistically, more men than women suffer from these defects.

Eye and brain - a good team

So color is not just there. It only arises in the moment of seeing. Our perception of color consists of the cooperation between the eyes and the brain.

Our brain receives and processes the light and brightness impulses according to a special order system, better than any computer in the world.

Every moment we see is continuously reprocessed and interpreted. This is how we can perceive color.

The system of perception is so complicated that, to this day, no one has been able to explain it precisely.