Light rays which are reflected by any surface become polarised and the Hoya HD CPL 52mm Filter PL-Cir Circular Polariser is used to select which light rays enter your camara lens. They allow you to remove unwanted reflections from non-metallic surfaces such as water, glass etc.  This filter also enable colors to become more saturated and appear clearer, with better contrast. This effect is often used to increase the contrast and saturation in blue skies and white clouds. The Hoya HD CPL 52mm Filter PL-Cir Circular Polariser does not affect the overall color balance of a shot.