'Optics' means 'belonging to seeing' (Greek) and is also called the science of light. Because of our concentration on the motor vehicle, we are more concerned here with technical than physical optics. This naturally includes the propagation of light, e.g. through reflectors, lenses and apertures. This is a range of electromagnetic radiation that is so close to our sensitivity to vision.

The loss of hearing is said to rob people of more quality of life than blindness, but a person healthy in this respect would spontaneously see the opposite. The insight that seeing is not possible without light seems trivial. It is not the direct source of light that accompanies us the most, but what is illuminated by it. And the medium that must be penetrated by the rays of light, the air, also plays a role.

In relation to the universe, we also call this air the atmosphere, which must be passed by everything that comes from outside. Obviously, the sun's light rays are particularly good at this, which is why it is the most important source of light. As you can already see from the fact that you should not look directly into it, it is more about what reflects light. Only then, the light rays reach our eye.

Somehow it has specialized in this frequency range during the course of evolution, which is the strongest of the sun's electromagnetic radiation and therefore best passed through the atmosphere. Of course, light can come directly from all kinds of sources. But even those that only reflect light can be perceived as light sources. On a bright day, there is basically only one light source outside, everything else are reflections.

The different colours are also created in this way. Because all the necessary frequencies for white light are present in the light of the sun, a reflecting surface only needs to fade out certain frequencies, e.g. due to its nature, i.e. it does not have to reproduce them with the same intensity as received, and already it appears coloured. If this applies to the higher frequencies of light, i.e. the red colour component, our eye perceives this as a mixture of green and blue, a kind of turquoise (cyan). Conversely, red is obtained by subtracting green and blue.

RGB is the keyword even for the simplest programming projects, e.g. for the Internet. The first two zeros refer to the red part, the next two to the green and the last two to the blue part, but hexadecimal beyond '99' to 'FF', which corresponds to '255'. So you don't have to be satisfied with jumping from 'Red' to 'Dark Red'.

Color is therefore in principle always the finest scattering mixture for light rays containing all frequencies. That is why they have a different effect every time they hit only certain frequencies. If you irradiate a red wall with green light, it turns black. Colour therefore depends not only on the nature of the surface, but also on that of the incident light. It must already contain the frequency that is to be brought out on the surface.

This is easily noticed in car headlights. Simple incandescent lamps give a different light than those with halogen technology and yet others that are generated by LEDs or lasers. Difficult for recording devices. You still know it from the red cast of analog Kodak cameras. Digital cameras work here with a white balance. This is how one wants to get a grip on the so-called color temperature, higher e.g. with more red content. Advertising often uses this quite deliberately.

And since paintwork can also age, it is particularly important for a refinish to be inspected under the same lighting conditions and even at the same viewing angle. Colour components can be faded out by scattering. When we speak of absorption, we are only emphasizing that a certain proportion has not reached the eye. Glass, which is generally not very absorbent, can cause so-called light refraction due to non-parallel surfaces of light entering and leaving it.

If this spectrum is then thrown against a white wall, all the colours of the rainbow are obtained. Such a thing sometimes appears under the same name in the sky, e.g. after a rain, from where the name also comes. Drivers experience light scattering mainly unpleasantly as fog, which then tries to infiltrate the correspondingly low mounted mockweifer.