Hoya 67mm NDx400 HMC Filter The Hoya 67mm NDx400 HMC Filter is a solid neutral density filter that enables a 9-stop increase in exposure length. The optical 2.7 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. By slowing your exposure time or increasing your aperture, you are able to control the depth of field and convey movement more easily. This filter features a three-layer HMC multi-coating, which provides 98-99% light transmission and helps to reduce internal flare and reflections. It is constructed from high-quality optical glass for notable image clarity and is set in a durable aluminium filter ring. Features: 2.7 ND filter darkens the image, allowing you to photograph with a slower shutter speed or wider aperture than normally required. Providing a 9-stop reduction, this filter allows you to control depth of field and convey movement more easily. Three-layer multi coating helps to minimize internal reflections and ghosting and maintain an overall neutral color balance.