Circular polarizing filters allow photographers to achieve creative, in-camera effects that are not possible after the image is created. A polarizing filter filters unwanted reflections from non-metallic surfaces such as water or glass, as well as light that reflects moisture and pollution in the atmosphere. By rotating the ultra-smooth filter, you can select just the right amount of filtering needed for the creative effect. KEY FEATURES OF THE HOYA PRO1 DIGITAL CIR-PL FILTERS Digital, multi-coated filters significantly reduce the appearance of flare and ghosting caused by reflections. The filters feature a black matte aluminum frame with a satin almit finish that reduces reflections. Low Profile Frames Ultra-thin filter frames to prevent vignetting on super wide-angle lenses are also designed to hold a lens cap. These filters feature a straight knurled edge for non-slip, easy attachment and removal.