This filter allows you to remove unwanted reflections from nonmetallic surfaces such as water, glass, ect. It also enables 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. Overall color balance is not affected by this filter. Designed for use with autofocus cameras that employ semi-silvered mirrors or prisms to split the light entering the viewfinder in order to calculate exposure and focusing distance.