This application calculates the exposure and shutter aperture with ND filter and ISO shooting.In photography, a neutral density filter or ND filter can be a colorless (clear) or grey filter.The purpose of standard photographic neutral density filters is to allow the photographer greater flexibility to change the aperture, exposure time and/or motion blur of subject in different situations and atmospheric conditions.For Pro version, instal "ND Filter PRO"In the version "ND filter PRO" you will find more exposure time and nd filters of various brands.