Hoya 49mm ND2 ND4 ND8 Neutral Density HMC Filters - 3 Piece Filter Kit in Original Packaging + TheImagingWorld Micro Fiber Cloth 2x = ND.3 (exposure adjustment = 1 stop, reduces ISO 1/2) -- 4x = ND.6 (exposure adjustment = 2 stops, reduces ISO 1/4) -- 8x = ND.9 (exposure adjustment = 3 stops, reduces ISO 1/8) To enable slow shutter speeds to be used -- To decrease depth of field by allowing wider apertures to be used To decrease the effective ISO of high speed film (ie: above ISO400) and allow it to be used outdoors in blight situations. To allow cine and video cameras to film subjects such as snow, sand or other bright scenes which would normally cause over-exposure. Includes Original Hoya NDx2, NDx4, and NDx8 Filters, All Filters are in Separate, Original Manufacturers Packaging + TheImagingWorld Micro Fiber Cloth