Neutral Density Filter(NDF)£º Application: Imaging Systems,Measuring Instruments Substrate: Soda-lime glass Thickness:0.7,1.1,1.9mm Surface Quality S/D:20/10,40/20,60/40(typical),80/50 Spectral Data waverange:400~700nm Optical Density Tolerance:¡À5£¥ Optical Density:OD0-OD4 Default effective aperture:>90£¥ Circular Variable Density Filter(CVND)£¬Linear Variable Density Filter(LVND) The main purpose of using neutral density filters is to reduce the amount of light that can pass through the lens. As a result, if a shutter speed is kept the same, after adding a neutral density filter, a larger aperture must be used to obtain the same exposure. Similarly, if an aperture is kept the same, after adding a neutral density filter, a slower shutter speed must be used to obtain the same exposure. Neutral Density filters appear gray and reduce the amount of light reaching the film,yet they have no affect on color balance. In conditions of extreme light intensity,such as sunshine on snowy mountains or on the beach, or when using a camcorder,ND (Neutral Density) filters are recommended.