Tiffen's Magnetic Control System technology, the MCS Variable ND Filter offers 1.5 to 10-stops of neutral density with quick and easy attachment. Simply thread the magnetic adapter into the front of the lens and snap the magnetic filter into place when the time comes. Neutral density filters offer a way to maintain control over depth of field and create special effects. A variable density filter eliminates the need to carry several individual filters. The heavier the density, the longer the exposure, allowing for movement effects like blurred water or streaking car lights in traffic. The filter also allows users to access wider apertures in bright lighting conditions.