Figure 8-11.--The additive primaries.

another color is produced. Green and blue produce

A special lens called the zoom lens is used for

cyan (greenish blue). Blue and red produce magenta

special effects. This lens can be varied from the

(bluish red). Red and green produce yellow.

normal visual coverage to distant closeups. In some

installations the lens is manually adjusted, while in

The combining of two primary colors, in

other TV cameras it is motor driven. The lens may be

proportional amounts, produces the new color.

adjusted either manually or by an automatic

However, when all three colors are combined as units

motor-driven device.

and in percentage of color, the result is white. Note the

following combination:

COLOR TV

One red unit represents 30 percent red

One green unit represents 59 percent green

It is known that normal vision is in color. The

human eye, in association with the brain, picks up the

One blue unit represents 11 percent blue

reflected light and imagines the scene in color. When

When one unit of green is combined with three

you view a colored painting, the object appears as a

units of red, the result is orange. By changing the

solid section of color. But, upon close inspection, it is

proportions of red and green, a variety of colors

seen that what appeared as solid color is really

between red and green can be produced. As the

individual brush lines. The same method is used in

proportion of the primary color mixture changes, the

television to make color appear solid on the face of a

resultant color also changes.

picture tube. Small spots of color instead of brush lines

make up each solid color.

The color by itself is called the hue. Green leaves

have a green hue. A red apple has a red hue. Different

PRINCIPLES OF COLOR

hues result from different wavelengths of light. Red

has the longest wavelength; violet has the shortest.

The principles of color presented in the following

The term saturation indicates how little a color is

paragraphs apply specifically to the development of

diluted by white light. The more a color differs from

color television pictures.

white, the greater its saturation. A weak blue color has

The three primary colors (fig. 8-11) used in

little saturation, while vivid blue is highly saturated.

television are red, green, and blue. When two primary

Saturation is interchangeable with the terms purity and

colors are combined, they produce another color.

chroma.

Figure 8-11 shows three large circles that

The brightness of a color as perceived by the

represent the three additive primary colors. In the

human eye is called luminance. The human eye sees

center where all three overlap, the color white is

brightness increase from blue to a peak at green and

formed. In sections where two primary colors overlap,

then decrease again to red. This apparent response

curve is the standard CIE (International Commission

of Illumination) luminosity (brightness) curve.

Color resolution is the full three-color reproduc-

tion of the red, green, and blue primaries.

Monochrome (black-and-white) reproduction is used

for the smallest details. For example, in the televised

picture of an automobile, the entire body of the car

would be in full color. Narrow vertical strips on the

frame might be reproduced in two colors, while the

outline of the car where it joins the background would

be in black and white.

TRANSMISSION

The camera unit used for color pickup is similar

to the black and white camera. However, the color

camera unit (fig. 8-12) has three pickup tubes (one for

Figure 8-11.--The additive primaries.

8-14