Hoya Pol-Linear Filter

Light reflected from electrically non-conductive surfaces is polarized to varying degrees depending on the angle of incidence, meaning its vibrations are not evenly distributed in all directions but are preferentially aligned in a plane. A polarizing filter allows such light to pass through, attenuates it, or blocks it, depending on the orientation of the filter relative to this plane. A linear polarizing filter is recommended for your SLR camera when it does not use partially reflective glass or prisms in front of the AF sensor and the exposure metering line.