This is the Lee Blue 20 CC Filter (Poly) for 3.9 inches (100 mm) System [LEEB100CC20B]
The filters in this range can be used either in front of or behind the lens, and reduce the transmission of light at specific wavelengths. Their primary use is to color balance films, however, the effect of each filter must be determined by tests or specified by the film manufacturer. They are also useful for correcting light sources for which no standard conversion filter exists, or for introducing a deliberate colour bias. Polyester filters are flexible films. ters, generally used for color. They are only available as standards, but are considerably cheaper than resin filters in most cases and can easily be cut to fit smaller filter systems. ... Contact us if you need more help.