The Formatt-Hitech 4 x 4" hard-edge neutral density 0.9 graduated glass filter helps to specifically darken skies and other bright areas of the image. The filter is densest at the edge and fades towards the middle, with a sharp transition line between the density areas and the clear areas. By having only a neutral density portion on the filter, you can selectively darken areas of an image whilst allowing the part of the image in the clear section to receive normal exposure. Neutral density filters do not affect image colouration and the 0.9 density provides a 3-stop reduction of light entering the lens. Formatt-Hitech glass filters are manufactured from high-quality Schott Superwite glass for exceptional clarity and maintained light transmission. This filter is compatible with the Formatt Hitech 100 mm filter holder and measures 4 x 4" / 101.6 x 101.6 mm. - Hard-edge ND 0.9 graduated filter for darkening skies and other bright areas of the image. - Provides a 3-stop reduction of light in selective areas. - The hard-edge transition is ideal for situations where there is a clear and distinct separation line between the bright and dark areas of the image. - Neutral density filters do not affect the overall colouration of the image. - Compatible with the Formatt Hitech 100 mm filter holder.