A circular polarizer helps to reduce reflections and glare by filtering out light that has become polarized. The polarizing filter can create effects such as darkening blue skies and focusing the edges of clouds. The filter will also reduce reflections on water and glass.
B+W S03 E Circular Polarizer is vacuum coated with one layer of anti-reflection coating, which helps to prevent internal ghosting and reflections. This filter has a filter factor between 2.3 and 2.8 (approximately 1-1.5 stops of light loss) The filter ring is made from brass with a female thread enabling more filters to be stacked. Note that vignetting may appear with any lens less than 20mm on a full frame camera body.