ND filter is also called neutral density filter. It can reduce and modify intensity of all wavelengths or colors of light equally, giving no changes in hue of color rendition. So it can realize real reappearance on the contrast of the scenery.The Fader ND filter can let the photographer use a larger aperture with a slower shutter speed to take the photo. When the photographer takes the image in the glare, the photographer can have the freedom to control the depth of field. It can also avoid the problem of diffraction caused by the extreme small aperture with a slow shutter speed. The main purpose to use ND filter is to prevent overexposure. If the light is too bright, it is very difficult to choose a slower shutter speed to take the photo. The ND filter can reduce the lights entering the lens, we can shoot the flow of water, the floating clouds, the moving crowds, the night scenery, even some special effects which our eyes couldn’t see with a slower shutter speed. NiSi Fader ND4-500 is a newly developed product based on NiSi Fader ND2-400. Its function is more powerful. NiSi Fader ND4-500 has three exclusive product patents. Glasses adopt superior optical glasses from AGC in Japan and SCHOTT in Germany.All Materials Used in this filter Meet the Requirements of European Union’s standards of Environ Ment Protection-ROHS(Restrictions on Hazardous Substances).