According to my research and the manufacturer's specifications, it is an effect filter for smooth transitions etc. and not a black crap filter. The manufacturer's specifications:
The JetMag Pro Pure Mist 1/4 (82MAG) filter reduces unwanted lens flare and minimises contrast for an even and natural image effect. It ensures smooth transitions, reduces wrinkles and conceals skin imperfections for a soft, filmic look. Thanks to the ultra-thin frame, vignetting is avoided even with wide-angle shots. Ideal for photographers and videographers who want a subtle, soft image aesthetic without distortion or excessive loss of contrast.