An ND filter is a light reduction filter. When shooting, when the ambient light is too strong, an ND filter is used. Can play a good role in reducing the amount of light. ND has different specification values, and different specification values reduce the amount of light differently. this set has ND4, ND8, ND16, ND32. the larger the value, the greater the reduction in the amount of light. for example: ND8 is darker than ND4. Different light environments can choose different ND values.