Service manual

STP 11-25R13-SM-TG
S - 14
(1) When a secondary color is combined with its complementary primary, white is produced. For
example, combining yellow with blue produces white. Cyan added to red produces white and magenta
plus green gives white.
(2) Carrying this one step further, the complementary colors added together produce white.
Specific proportions of these colors must be used in order to produce white.
c. Producing Colors
. Since yellow + blue = white, and red + green = yellow, then red + green +
blue = white. Since the addition of the three primaries can produce white, the addition of the correct
proportions of the three complementaries, which are made up of the three primaries, can also produce
white. Therefore, cyan + magenta + yellow = white.
(1) It is not necessary to overlap the primary colors in the additive process to produce a different
color. Two sources of colors may be placed near each color; at a certain viewing distance the two colors
will blend and produce the new color. The eye actually performs the additive process.
(2) The screen of a color CRT contains hundreds of thousands of phosphorous dots arranged in
triangular patterns as shown in Figure S-12. Its own electron beam excites each dot. The cluster of dots
can emit a white light or any other color depending on the strength of the various electron beams. Due to
the limits of vision of our eyes and the process discussed above, we are actually seeing an illusion when
we watch our television receiver.
d. Brightness of Colors
. Each additive primary contributes a certain percentage of the brightness
in the white that results from mixture. 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 of the other 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.
(1) Therefore, when combining green with red we have yellow with a brightness value of 89
percent. Cyan has a brightness value of 70 percent. The third complementary color, magenta, has a
brightness value of 41 percent. It obtains 30 percent from red and 11 percent from blue. Figure S-13
shows the order of brightness, which is known as the luminance stairstep.
Figure S-13. Luminance Stairstep
(2) In the development of a color matching and specification system, extensive color matching tests
on many observers were conducted using a device known as a colorimeter. In order to establish an
average that could be considered as that of the standard observer, many individuals performed similar
tests. The results of these tests are known as tristimulus values for color mixture curves. By the use of
mathematics equations, the information contained in the color mixture curves has been converted to a
graphical representation of color on a three-dimensional plane and is referred to as the Maxwell triangle.