Color Compensating Filters
Color compensating filters are sometimes referred to as CC filters. They are used to adjust the overall color balance received from color films, especially in slide film.
Improper color cast can occur in your photos without one of the color compensating filters. The filters are generally used to color balance lights such as fluorescent, tungsten, and mercury-vapor and also to bounce light that is reflected from colored surfaces and objects.
Color compensating filters are also used to balance unusual circumstance lighting effects, like underwater lighting. These filters can be used to compensate for known color deficiencies in unexposed color films. They can also be layered when you are mounting a color transparency to compensate for off color hues.
Color compensating filters can range in price from about $35 to $400. They come in various sizes.