Made out of high quality optical glass the lee 75x90mm seven5 big stopper is a long exposure nd filter designed to reduce the amount of light entering the lens by up to 10 f stops by greatly extending exposure times the seven5 big stopper has the effect of allowing anything that is moving in your image to become blurred or ghost like eg clouds water etc however the effect is not limited to landscapes and can also be used on cityscapes to blur moving people or cars the big stopper fro