Neutral Density filter reduces intensity of all wavelengths or colors of light equally, giving no changes in hue or color rendition. The purpose of standard photographic neutral density filters is to allow the photographer greater flexibility to change the aperture, exposure time and/or blur of subject in different situations and atmospheric conditions. Instead of reducing the aperture to limit light, the photographer can add a ND filter to limit light, and can then set the shutter speed according to the particular motion desired and the aperture set as needed. With the Zomei variable range ND filter, you can enjoy total control of virtually any light environment. Simply turn its exterior ring to access any of ND settings without wasting time changing or adding filters.