The Heliopan 77mm Variable Grey Neutral Density Glass Filter ( 1-6 Stops) 705890 can reduce the exposure on your camera anywhere from 1.0 to 6.6 f/stops. When shooting with high ISOs, this filter can allow you to shoot under bright lighting conditions like on a snowy mountain or at the beach. This is also an ideal filter for creating long exposure special effects such as capturing the "blur" of running water. It also permits you to control your depth of field by helping isolate your subject from its background by using a wider aperture. A convenient index scale on the filter ring makes exposures repeatable and exact.