The LEE Filters 100 x 100mm Little Stopper 1.8 Neutral Density Filter is a solid neutral density filter providing a 6-stop reduction in exposure. This 1.8 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. By slowing your exposure time or increasing your aperture, you are able to control depth of field and convey movement more easily. This filter is constructed from a high quality optical glass for high definition and clarity. It is compatible with the 100mm Filter System, which is designed for use with most lenses and camera types. This filter measures 3.9 x 3.9" / 100 x 100mm. At six stops, the Little Stopper is ideal for those low-light conditions at the beginning and end of the day (when the Big Stopper's ten stops may prove too much), allowing you to enjoy increased flexibility with exposure lengths. In many shooting conditions, this means that detail and texture in areas of movement such as the sky and water would be retained, while still conveying a sense of time passing.