The hitech firecrest irnd 77mm 48 neutral density nd filter reduces the light reaching the sensor by 16 stops allowing you to use longer shutter speeds and increase aperture the increase in aperture small fnumber gives you more control over depth of field and a longer shutter speed creates a time passing blurred effect which is often used in landscapes this filter features a 15 layer firecrest multi coating which is applied directly to the glass and helps minimise reflections and flar