The ACCU-ND technology in the Hoya PROND filters yields a truly neutral color balance that will not add any noticeable color-cast to your images. The Hoya PROND series is aimed at the still photography and HDSLR video markets. The Hoya Pro ND 500 Filter absorbs the light entering the lens evenly across the visible spectrum and reduces the amount of light entering the lens by up to 9 f/stops without affecting the color balance. Reducing the amount of light allows the use of wider apertures and slower shutter speeds for creative and dramatic effects. ND filters are widely used by landscape photographers who want to capture smooth, flowing waterfalls or seascapes but still retain the correct exposure throughout the whole photograph. Alternatively, ND filters can be used to reduce the depth of field and enable the use of wider apertures to ensure your subject is crisp while the background becomes a soft blur - great for portraiture. ND filters also allow cine and video cameras (which have fixed shutter speeds) to film subjects such as snow, sand or other bright scenes which would normally cause over-exposure.