Rosco Cal Color Filters This series of color effects lighting filters is designed specifically to the spectral density of color film. Cal Color filters adjust the transmission of these color components at the individual light source so you can correctly predict how your film will render. For instance, a Cal Color 90 Green selectively enhances green transmission by reducing the effective blue & red transmission by three stops. Each color is designed in four densities: 15, 30, 60 & 90, corresponding to the familiar ½, 1, 2 & 3-stop calibrations.