Lee Filters 0.6 Graduated Neutral Density Filter, 150x170mm Resin for SW150 Holder, Hard Edge To enable slow shutter speeds to be used, especially with high speed films, to record movement in subjects such as waterfalls, clouds, or cars To decrease depth of field by allowing wider apertures to be used, which helps separate subjects from their background To decrease the effective ISO of high speed film (above ISO 400) and allow it to be used outdoors in bright situation To allow cine and video cameras (which have fixed shutter speeds) to film subjects such as snow, sand or other bright scenes which could cause overexposure