Formatt 3 x 3" CC 20Y Yellow Color Compensating Filter or CC's act as sponges, absorbing excessive amounts of particular colors. Some photographic situations require specific color corrections. For example, when shooting daylight film under fluorescent lighting, some magenta correction is needed in order to remove the greenish tint that would otherwise appear.
Formatt CC filters offer color control of primary (red, green, blue) and secondary (yellow, magenta, and cyan) levels. Densities range from 0.025 to 0.50; by combining different densities, it gives the flexibility to knock out specific colors as well as offering extremely fine adjustments in color temperature.