The Tiffen Variable Neutral Density (ND) Filter - 2 to 8 Stop is a versatile and flexible tool, affording you the convenience of using several Neutral Density filters all in one. Primarily used as a photographic tool for controlling depth of field and exposure, the Variable Neutral Densityis being sought in the video market as well because it is fast, easy to use, small and light-weight, and does not require additional accessories such as a matte box. The Tiffen Variable Neutral Densityfilter operates on the same principle as a Circular Polarizer - rotate until you reach your desired effect and shoot. It allows you to have continuous control over the amount of light coming through your lens in an approximate range of 2 (Neutral Density0.6) to 8 (Neutral Density2.4) stops - while maintaining the integrity of your image. Note: The evenly spaced indexing marks between MIN and MAX do not represent calibrated stops. They are for reference only, to be used as a density bench-mark to return to a previous setting.