B+w ND Varo (1 to 5 stop) MRC filter reduces the amount of light entering the camera lens by one to five full f-stops. The amount of stop loss is controlled by turning the rotating filter ring. This allows an increase in depth of field by enabling you to open the lens One to five f-stops or one to five stops slower shutter speed without changing camera ISO/ASA setting. For example if you can achieve proper exposure at 1/60th shutter and F/5.6, then the b+w ND Varo will allow you to achieve 1/60th at f/4.0 to f/1.8 for increased depth of field. The variable neutral Density setting on this filter will allow for maximum versatility and cut down on filter changes in the field, as the light changes so can your filter setting.The multi-resistant-coating (MRC) is a proprietary 7 layer process developed by schneider-kreuznach in Germany and allows for maximum image quality and prevents ghosting and reduces Reflections. 99.5% of the original light that enters the lens is passed by the MRC coating. This filter Also features b+w Nano coating which is an additional 8th layer of coating for superior ease of cleaning. The molecular Structure of the Nano coating is smaller than a drop of water making water bead and fall off the filter surface.The ring is constructed from Brass which greatly reduces/eliminates the filters' Chance of the filter being stuck to your Lens because it is a dissimilar material to most lens filter mounts. Temperature changes such as moving a filter from the warmth of a camera bag to extreme cold Can cause normal aluminum filter rings to expand and contract causing them to "stick" To the lens front. The brass construction of b+w brand filters resists temperature changes and will not contract or expand preventing the filter from catching on the lens front. Brass ring construction also prevents cross-threading on the lens.this filter features a slightly larger outer diameter so certain Manufacturer provided lens hoods may not fit properly.