The sigma 49mm dg multi layer coated circular polarizer 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 polarizer differs from a linear polarizer in that it contains a quarter wave plane in addition to the linear polarizing filter the addition of th