The Rosco 20 x 24" CalColor #4315 Filter (15 Cyan) is a color effect lighting filter designed specifically to the spectral sensitivity of color film. This color is designed with density of 15 corresponding to the familiar 1/2 stop calibration. In color photography, three light-sensitive emulsion layers separately record the individual blue, green and red components of the spectrum.CalColor filters adjust the transmission of these color components at the individual light source in a familiar and reliable manner. As a result, the cinematographer can exercise selective and predictable control over the image's coloration as rendered by the film.