The Tiffen 4 x 5.65" Graduated 0.9 ND Hard Edge Filter (vertical orientation) is a graduated neutral density filter that helps specifically darken skies and other bright areas of the image. The filter is densest at the edge and fades to clear in the middle, with a sharp transition line between the dense and clear areas. Neutral density filters do not affect image colouration and the 0.9 density provides a 3-stop reduction of light entering the lens. This filter is manufactured using ColorCore technology, a process that involves laminating the filter substrate between 2 pieces of optical glass and polishing it flat to a tolerance of 1/10,000th of an inch. This filter measures 4 x 5.65" / 101.6 x 143.5 mm. Note: The transition line of a vertically oriented filter is parallel to the short side of the filter. - 0.9 ND hard edge graduated filter for darkening skies and other bright areas of the image. - Provides a 3-stop reduction of light in selected areas. - Neutral density filters do not affect overall image colouration. Specifications