A polarizing filter removes unwanted reflections from non-metallic surfaces such as water and glass. They also enable colors to become more saturated and appear more clear, with better contrast. This effect is often used to increase the contrast and saturation in blue skies and white clouds. Polarizing filters do not affect the overall color balance of a shot.

A circular polarizer filter (CPL) is generally required if you want to use the "auto-focus" feature in your camera.  If you are manually focusing your camera, you may be able to save some money by using a less expensive linear polarizer

These filters are for all video, still, digital and film cameras.

The following filters are for wide angle lenses. 

These filters only have threads on one side and you cannot use a standard lens cap or stack another filter on top.