Circular Polarizer (CPL) for Pentax 90mm f/2.8 D FA 645 Macro ED AW SR Lens

Slim aluminum frame designed to prevent vignetting while still allowing full rotation for exposure and effect adjustments. A nonslip upper rim makes the filter simple to mount, rotate and remove. Optics feature double-sided, multi-layered coatings and are anti-oil, anti-dust, anti-soil, scratch & water resistant. This circular CPL reduces unwanted reflections from non-metallic surfaces like water and glass, while boosting color rendition and overall contrast. Commonly used to intensify blues in the sky and deepen white cloud detail, it also cuts atmospheric haze in distant landscapes to produce richer, more vivid colors. The filter works by arranging and filtering directionally polarized light perpendicular to reflected light so much of that light is absorbed; the effect is strongest when used at a 90° angle from the sun.