Product Highlights: The Hoya 40 mm Neutral Density (ND4) 0.6 Filter has several uses and offers the possibility to achieve otherwise unachievable results. ND filters appear gray and reduce the amount of light reaching the film. They have no effect on color balance. Multi-coated to minimize reflection at the filter surfaces which reduces flare and ghosting. Neutral Density filters have four main uses To enable slow shutter speeds to be used, especially with high speed films, to record movement in subjects such as waterfalls, clouds, or cars