The Big Stopper is a powerful 10-stop neutral density filter from Lee filters. The name has caught on and many now refer to high powered ND filters as ‘big stoppers’. The point of an ND filter is that it reduces the light passing through the lens and allows long exposures even in bright daylight. This is the technique used to create blurred water and cloud effects in landscapes.
Lee Filters also makes a Little Stopper, which reduces the light by 6 stops, and a Super Stopper which reduces the light by 15 stops.
Filters like the Big Stopper are typically used in square filter systems alongside other filters like polarizing filters or graduated filters, but it’s also possible to get round glass ND filters in various sizes, which are more compact and easier to attach.