Light rays which are reflected by any surface become polarised and polarising filters are used to select which light rays enter your camara lens. The Circular Polarising filter allows you to remove unwanted reflections from non-metallic surfaces such as water, glass etc. It also will enable colours 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 PROMASTER Polarising filter does not affect the overall colour balance of a shot. Great for use with all traditional and digital cameras.