LEE Filters SW150 Big Stopper
The Big Stopper is a neutral density filter that reduces the amount of light entering your lens by ten stops.
By greatly extending exposure times the Big Stopper has the effect of allowing anything that is moving in your image to become blurred or ghost like, for example clouds, waterfalls, rivers, and the sea. The filter can also be used on cityscapes to blur people or on roads and motorways to blur traffic.