Promaster 72mm HGX Prime Variable Neutral Density Filter A professional, world-class variable ND filter with 1.3-8 stops of density range, that provides a clear sharp image and is easy to use. This ProMaster HGX Prime VND filter mounts to lenses with 58mm threads and provides an exposure reduction of 1.3 to 8 stops (ND2.5-ND256 equivalent). It darkens the entire image allowing for slower shutter speeds and/or wider apertures with applications for both still photography and videography. Mechanical "hard" stops at each end of the filter's range prevent bypassing the minimum or maximum useable density. A small, knurled knob provides a tactile experience making it easier to rotate the filter quickly and smoothly, simply by touch. This Tactile Control Knob is removable if you prefer not to use it.White lines on the filter's ring indicate its density setting at each full stop. These lines represent specific densities of 2, 3, 4, 5, 6, and 7 stops with 1.3 and 8 stops being achieved at each end of the filter ring's range of travel (MIN and MAX positions). An additional "X" mark on the filter's ring indicates the density point at which cross polarization (X pattern) begins, slightly, to visually appear when using most wide-angle lenses (a phenomenon common to all VND filters). As an HGX Prime filter this 49mm variable ND is one of the finest in the world. Its Repellamax II coatings, optical glass, and color-corrected polarizing films (applied using a unique, super-secret, process) combine to provide an extremely sharp image with excellent color rendition as well as protection against moisture, oil, dirt, and dust. An incredible 36 layers of coatings are used in manufacturing this filter to a new, world-class standard!