Filters improve tone.
a. Filters are used to control the amount and type of light that reaches the film. Some filters
hold back a particular color of light, others block light reflected from smooth objects, and others simply
reduce brightness. You can stress any feature on a picture or de-emphasize that feature depending on the
b. Filters that prevent certain colors of light from reaching the film are used with black and
white film because even black and white film is sensitive in varying degrees to the color of light. Film
sensitivity to color is discussed later in this lesson. In this section we'll just say that two different colors
may or may not produce the same shade of gray on black and white film, depending on the type of film
and the colors.
c. If a filter completely absorbs a color, the light of that color does not reach the film and the
film sees darkness (dark gray on print). For instance, where a red shirt photographs as light gray without
a filter, the red shirt will be black when photographed through a filter that completely absorbs red.
Normally, the filter does not completely absorb the color so the red shirt would show up as a darker gray.
d. When the colors that the filter absorbs appear darker on the print, the colors that the filter
passes appear lighter.
e. When dealing with colors and filters, keep in mind that we are dealing with exposures onto a
negative which then must be printed onto paper. When photographing with transparencies we are
dealing with a reversal process. When the filter passes a color, that portion of the negative is dark.
When we print the negative, the dark portion of the negative holds back light and that portion of the print
is light in color (shade of gray). Conversely, if a filter absorbs a color, that portion of the negative is
light or transparent. When a print is made, the light passes through and is dark on the print.
Filters pass their own color. To select the proper filter, you must know a few simple facts about
a. Out of the vast number of colors, there are three primary colors -- red, green, and blue. They
are called primary colors because any other color can be formed from a combination of the three. The
picture you see on a color television set is actually three pictures, one red, one green, and one blue. All
the other colors you see are actually mixtures of these three colors of light. A similar process is used to
produce color photographs.