e. Each additional primary color contributes a certain percentage of brightness
in the mixture of white. Green is the brightest of the three primaries, red is the
second brightest, and blue is the dimmest.
This has been determined through
experimentation with the response of the eye. The eye responds more to green than
any other of the primary colors. With the total brightness of white considered as
unity, green contributes 59 percent of the total, red 30 percent, and blue 11
percent. Therefore, when combining green with red we have yellow with a brightness
level of 89 percent.
Cyan has a brightness value of 70 percent.
complementary color, magenta, has a brightness value of 41 percent. It obtains 30
percent from red and 11 percent from blue. The order of brightness for each color
is known as the luminance stairstep (fig 1-8).