الألوان والعين البشرية .. كتاب التلفزيون الملون والعادي

2-3 Colors and the human eye

The green color signal Eo has the essential role in shaping luminance. This is consistent with the specifications of the human eye, whose sensitivity is as great as possible for the greenish-yellow color with a wavelength of (551 nanometers), and this sensitivity decreases as we move away from this field (Figure 3-4).
They are less sensitive to red than green and to blue less than red. The human eye also has another advantage, which is that it does not distinguish shades of colors unless the visible spot has a relatively large area - if this spot is small, then the eye finds it difficult to distinguish between colors - but if the spot is very small. The eye can only distinguish degrees of color change. You see the colors in gray as if the eye has color blindness. The result is that large objects or areas must contain the three primary colors, to suit the comfortable vision of the eye - while in medium objects or areas, it is sufficient for the eye to have two different compound colors to cover the range of colors - but if the spot or area is very small, then the eye does not distinguish the color, but Distinguish only a change in lightness or luminance of color

It is these properties of the human eye that dictate that television systems and their designers must take into account them in order for the television picture to appear clear, clear, and acceptable. This will become clear when studying the system PAL, SICAM and NTSC, and the different methods of encoding in transmission, and decoding this encoding in reception.