The 77mm ND Tiffen Variable Neutral Density Filter is a unique, versatile and flexible tool that provides the convenience of multiple ND filters in one. The Variable ND, which is mainly used as a photographic tool to control depth of field and exposure, is also in demand in the video market because it is fast, easy to use, small, lightweight and does not require additional accessories such as a matte box. The Tiffen Variable ND filter works on the same principle as a circular polarizer - rotate until you achieve the desired effect and shoot. This allows you to continuously control the amount of light passing through the lens over an approximate range of 2 (ND 0.6) to 8 (ND 2.4) stops, while maintaining the integrity of your image. Note. Evenly spaced index marks between MIN and MAX do not represent calibrated stops. They are for reference only and should be used as a density reference to revert to previous settings.