Color and vision

1. Nature of eyes to light

The electromagnetic wave which human eyes can perceive ( wave length approx.380 micro to 780 micro ) is called visible ray of light or light. The perception depends on wave length, and only light with a curtain range of wave length can be seen as colors.
Three element of colour
- luminance ( brightness)
- hue ( tint )
- saturation
Brightness means lightness of colors. When it is light, we say high brightness, and when dark, we say low brightness. Hue ( or tint ) is veriety of colors such as red, green and blue, which depends on wave length. Saturation means density of colors, which indicates the rate of how much is white light mixed.

2. Mixture of light

Red, green and blue are called color primaries, because they can not be made by mixing other colors.
In color TV receiver, to perform mixture, 3 colors of red, green and blue dots are aranged regularly on phosphorescent screen.

3. ICI chromaticity diagram
ICI ( international cnmmision on illumination ) , in which all the colors are included. In color tv, the point of R, G and B, are decided depending on emitting colors of phosphors. The inners part of the triangle encircled by the 3 points is called color area. The colors other than the triangle cannot be made, whatever proportion of the 3 colors is taken for mixing.

4. Nature of eyes to colors
If the area ìs large enough, all thers can be displayed as mentioned above. In color tv receiver, brightness and choramacity signal are transmitted at the same, for large areas ( vidio signal in charge of 0―500kHz ).