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Loading ... The light
The color has no physical reality, it exists in our brain because our eye is sensitive to light is a sensation.
For an image exists, it is initially a light source that illuminates an object. The object reflects the light rays to the eye of the observer. The observer sees the light rays that the nervous system must decrypt to restore the original appearance.
The transmission of light rays are distorted by the medium through which it passes. We do not see the same way the light of a flashlight at night or in broad daylight, in fog or in summer in a desert or lost in the middle of a street lighting. Are present the eye with its photoreceptor cells, light and objects of nature or man-made.
The eye
The human eye is a vision device that can be compared in its operation, a digital camera: it has an optical portion to form a sharp image on a surface sensitive to light, the retina.
The retina is composed of cells transforming information received light into electrical impulses transmitted to the brain.
These cells are of two types: rods and cones.
Rods are sensitive to movement and low levels of light, but they do not see colors. The surface of an object absorbs some light radiation it receives and reflects others. Our eye then receives the reflected radiation. These are reflected radiation that will determine the color of that object.
Then we say that an object "is red" because its surface reflects the red light and absorbs all others.
The same object will be "black" if you light it with a green light for example. This radiation is absorbed, the surface of the object does not reflect anything!
The cones on the other hand are sensitive to color and are active at a higher level of light. Three types of cones can collect all of the light spectrum known as "visible" and react either blue or green or red.
These three "stimuli" different (red, green, blue) that will excite the cones according to their different wavelengths. There are three types of cones, which transmit different sensitivity, brain, three different sensations:
- Sensation of color,
- Sensation of brightness (brightness more or less)
- Sense of purity or "saturation" (more or less bright or washed out).
The light
The portion of the electromagnetic spectrum we call visible radiation covers the wavelength range from 400 nanometers (blue) and 700 nanometers (red). Some animals look beyond this range in the ultraviolet and infrared. It is the same for some photographic film or graphic arts (films for infrared shooting night, for example).
Objects
The concept of color is the result of reflection of visible light on an object to our eye. A general principle governing this reflection: A colored surface (every object is a colored surface) transmits (passes) or reflects its own color and absorbs his (or her) color (s) further.
For example, if a printed surface is illuminated (or colored) in blue, the surface reflects the blue (a mixture of cyan and magenta) present in the light that illuminates, and absorbs against the yellow (mixture of green and red) present in the same light.
The visible spectrum
The decomposition of sunlight (white light) by a prism allows us to obtain the spectrum visible to the human eye. To use this spectrum in the color reproduction, it is said that white light (composed of all colors visible to the eye) is composed of equal parts of red light, green light and blue light.
In the tool is our vision eye cells sensitive to colors (cones) are respectively assigned to the Red, Green, Blue.
So we live in an RGB color system.
