This Variable Fader ND2-ND400 Filter from K&F Concept is a 49mm variable neutral density filter providing an adjustable light reduction of 1 to 8.6 stops. It darkens the entire image evenly, allowing a photograph to be made with a wider aperture or slower shutter speed than normally required. By slowing the exposure time or increasing the aperture, it is possible to control the depth of field and blur movement easily, creating a dynamic look for streams, waterfalls, landscapes, and more.