Absorption Filters - These filters are generally constructed of dyed glass, lacquered gelatin, or synthetic polymers (plastics) and have a wide range of applications. They are frequently used to create special effects in a number of photography applications and are widely employed in the cinema industry. In addition, absorption filters are commonly found in signs and traffic signals, as well as directional signals on vehicles such as automobiles, boats, and airplanes.
A typical absorption filter is illustrated above in Figure 1. In this example, a magenta filter that is designed to adapt to a camera lens is met by three incident light waves. Though they are illustrated as red, green, and blue waves, they are intended to represent all of the colors that comprise white light. Notice the filter selectively transmits the red and blue portions of the incident white light spectrum, but absorbs most of the green wavelengths. Remember, as discussed in the primary colors article, the color magenta is obtained by subtracting green from white light.