Rosco Calibrated Color is a series of color effects lighting filters designed specifically to the spectral sensitivity of color film.
The series includes the primary colors Blue, Green and Red, along with the secondary colors Yellow, Magenta and Cyan followed by Pink and Lavender.
Each color is designed in four densities: 15, 30, 60 and 90, corresponding to the familiar 1/2, 1, 2 and 3 stop calibrations.
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.