The lee sw150 150x150mm super stopper nd glass filter reduces the amount of light entering the lens by 15 stops its 45 density and 32 000 15 stop filter factor means that an ordinary 2 second exposure will take over 17 hours to expose through the filter allowing you to photograph with a wider aperture or slower shutter speed in bright daylight by greatly extending exposure times the super stopper has the effect of allowing anything that is moving in your image to become blurred or ghost li