Cokin P154 Filter, P, Grey Neutral Density 8X 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 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. ND8 - 0.9 (exposure adjustment = 3 stops, reduces ISO 1/8)