Light rays which are reflected by any surface become polarised and polarising filters are used to select which light rays enter your camera lens.   They allow you to remove unwanted reflections from non-metallic surfaces such as water, glass etc. They also 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. HOYA's polarising filters do not affect the overall colour balance of a shot.

   
               With out Circular Polariser                                          With Circular Polariser