: Hoya 77mm HMC ND8 Multi-Coated Neutral Density Filter : Camera Lens Neutral Density Filters : Electronics. To enable slow shutter speeds to be used to record movement in subjects such as waterfalls, clouds, cars, etc. 。 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 (ie: above ISO400) and allow it to be used outdoors in bright situations. 。 To allow video cameras (which have fixed shutter speeds) to film subjects such as snow, sand or other bright scenes which would normally cause overexposure. 。 77mm Neutral Density 0.9 8x Multi-Coated Filter 。 。 。