This is a kind of modern-day soft focus filter that takes a different approach. Black mist filters are designed to reduce contrast and soften harsh highlights in portrait shots, and at the same time soften wrinkles, spots and other unwanted facial blemishes.
Black mist filters are typically round filters that screw directly into the lens’s filter thread, as they would not normally be used in combination with other filters – though you can get black mist square filters for filter holders and filter systems. Revoring makes a black mist filter using its trademark spring-loaded multi-size filter thread mechanism for use with different filter thread sizes.