Available in 5 strengths 1,2,3,6 & 10 stop. Strong Neutral Density filters of 6 or 10 stops are used to create shutter drag effects by slowing the shutter speed during bright sunny days. For example a waterfall which looks misty from the flow of water. A 1 or 2 stop filter can be used to gain a more shallow depth of field when too much light prevents the aperture from being set to its widest setting.