The Tiffen 6.6 x 6.6" 0.9 Hard Edge Graduated Neutral Density filter is a graduated neutral density filter that helps to specifically darken skies and other bright areas of the image. The filter is densest at the edge and fades to clear at the centre, with a sharp transition line between the dense and clear areas. Neutral density filters do not affect the colouration of the image and the 0.9 density provides a 3-stop reduction of light entering the lens.nnThis filter is constructed from Water White glass and is made using ColorCore technology, a process that involves laminating the filter substrate between 2 pieces of optical glass and grinding it flat to a tolerance of 1/10,000th of an inch. This filter measures 6.6 x 6.6" / 167.6 x 167.6 mm.nnn- 0.9 hard edge graduated ND filter to darken skies and other bright areas of the image.n- Provides a 3-stop reduction of light in selected areas.n- Neutral density filters do not affect the overall colouration of the image.n- Water White optical glass for excellent clarity.nnnSpecificationsnnn