Figure 1-1. Cross section of negative film
Figure 1-1 shows a cross section of a typical color film. Starting at the top and working down
the diagram, an antiabrasion overcoating protects the film from minor abrasions. Next is the blue-
sensitive emulsion layer where the blue record is made and where yellow dye is formed during
processing. The next layer consists of a colloidal silver. It acts as a yellow filter to absorb blue light so
that only green is recorded in the orthochromatic layer. Magenta dye is formed during the process. Red
is recorded in the next layer, which is a panchromatic emulsion. This emulsion is manufactured with a
very low sensitivity to green light since the blue light is absorbed by the colloidal silver, only a red
record is made. Cyan dye is formed in the panchromatic emulsion layer during processing.
In effect then, a sheet of color film is made up of three separate layers, each one sensitive to or
able to record only one of the three additive primary colors of light. Subtractive colors, such as yellow,
are recorded in the two layers which form to make up the color (green and red). Green and blue light
make cyan, the complement of red. Blue and red light combine to form magenta, the complement of
green. These three complementary colors-cyan, magenta, and yellow, known as the subtractive
primaries, are the colors of the dye layers formed in an exposed and processed color negative (fig 1-2).