Made from high-quality optical glass, the LEE85 Big Stopper allows you to greatly extend exposure times, reducing the amount of light entering the lens by up to 10 stops and in doing so, you can produce unique and beautiful photographs. The LEE85 Big Stopper has the effect of allowing moving objects to become blurred or even ghost-like. Often photographers will use this effect on waterfalls, rivers, and the sea, capturing long exposures and turning the water milky. It's also used on cityscapes to blur people or on roads and motorways to blur traffic. It gives a sense of time passing by in your image, more so than a standard still image. The LEE85 Big Stopper also features useful thumb guides for you to easily position the Stopper square within the holder and when you're done, you can stow the filter safely in the included tin.