ND filters reduce the quantity of light that reaches the sensor ¨C or the film ¨C increasing the exposure time. These filters have 3 main practical applications: - emphasizing the flow of movement - reducing the depth of field - avoiding overexposure Technical Specifications of Zomei Grey Neutral Density ND2+ND4+ND8+ND16 Filter: Compatible with Cokin Z-PRO Series, need to work with Z Series holder and adapter ring. Recommended for: SLR or Full Frame or APS-C D-SLR cameras with wide-angle lens from95mm. Neutral Density ND2(0.3) reduces the light 1 full stop. Neutral Density ND4(0.6) reduces the light 2 full stops. Neutral Density ND8(0.9) reduces the light 3 full stops. Neutral Density ND16(1.2) reduces the light 4 full stops. What's In The Box? Full Color Grey ND2+4+8 filter.