b. A filter passes its own color and absorbs other colors. For instance, a red filter looks red
because of the red light coming through the filter. Green and blue objects look black through a red filter
because green light and blue light do not pass through a red filter.
c. Equal amounts of all three primary colors produce white, so white light is said to contain all
colors. Snow looks red when seen through a red filter because only the red portion of the white light
comes through the filter. The result of combining the primary colors in equal amounts is shown in
Figure 1-1.
Figure 1-1. Combination of primary colors
d. Combining two primary colors in equal amounts produces a secondary color. Red and green
produce yellow, red and blue produce magenta (a reddish purple), and green and blue produce cyan (a
light greenish blue).
e. A filter of a secondary color will pass both the primary colors that make up the secondary
color and combine to produce the secondary color. For example, a yellow filter will pass red, green, and
yellow but will not pass blue (fig 1-2).
Figure 1-2. Effect of filter on color
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