CPL Filter is used to select which light rays enter your camera lens. It can be used to remove unwanted reflections from non-metallic surfaces such as water or glass. Filter can also be used to saturate colors and provide better contrast. The effect can be seen through the camera viewfinder and changed by rotating the filter. The filter factor varies according to how the filter is rotated and its orientation to the sun. Filter factor is between 2.3 and 2.8 (approx. +1.3 stops). Typical applications include darkening skies, water reflection elimination, and window/glass/eyeglass reflection elimination. CPL filter are specifically designed for use with auto-focus SLR cameras (They will also work on manual systems and video cameras without problems). Linear polarizer filter may not work properly with auto-focus cameras. Each filter comes with a plastic storage box.