Service manual

STP 11-25R13-SM-TG
S - 20
(1) Y (Luminance) = 0.30R + 0.59G + 0.11B; where: Y = a mathematical symbol representing the
luminance signal, R = red signal, G = green signal, and B = blue signal.
(2) This particular proportion was chosen because it closely follows the color sensitivity of the
human eye. That is, if you take equal amounts of red, green, and blue light and superimpose the rays
from these lights on a screen, you will see white. However, if you look at each light separately, the green
will appear to be twice as bright as the red and from 6 to 10 times as bright as the blue. This is because
the eye is more sensitive to green than to red and more sensitive to red than to blue.
(3) Thus, the luminance signal is composed of 59 percent green signal (that is, 59 percent of the
output of the green camera pickup tube), 30 percent red, and 11 percent blue and contains frequencies
from 0 to 4.2 MHz.