Neutral Density (ND) filters can reduce the intensity of light without appreciably changing its color. Classic ND filters have different f-stop reduction numbers and transmittance thus generated can be applied for different shooting conditions, such as portraiture, water falls, etc. This innovative item brings great innovation of the filter industry. Through the polarization angle modulation (rotate the filter ring when operating), this lens can change the luminous flux substantially with freedom, reducing the ND number from 2 to 400! It can easily replace dozens of all grade of density ND gray filters The filter is made of two pieces of high polarizer (HPL) which has above 99.7 polarization and a precision rotary of the wide-angle lens ring. Please note the glass of this filter is made in Japan, and it is multi-coated. (a single coated will sell at better price)..