The cpl filter helps to reduce reflections and glare by filtering out light that has become polarized due to reflection from a non metallic surface this results in a noticeable increase in the saturation of skies and foliage as well as clearer imagery when photographing in hazy conditions a circular polariser differs from a linear polariser in that it contains quarter wave planes in addition to the linear polarising filter the addition of this quarter wave plane is to circularly polarise th