The Hoya Pro ND64 Filter is an ultra thin filter that permits you to shoot and create images that would not ordinarily be possible to capture. This filter effectively reduces your ISO by 1/64 (6 stops).This means that a shot normally taken at 1/500 sec @ f/11 can be shot at f/11 at 1/8th second. Designed with the outdoor shooter in mind, this filter helps reduce the amount of light entering the lens. This translates into the use of wider apertures and, thereby, permits the photographer to have more control over his depth of field. This is especially useful when shooting outdoor portraits when you wish to establish more of a separation between subject and background. The result will be a sharp, clear subject with a soft background. The ultimate value of this filter is its ability to allow you to use high speed ISOs under bright light conditions.