The Neutral Density Filters (ND4 ND8 ND16 ND32) are great for portraits and outdoor scenes in strong sunlight. They reduce the amount of light reaching the film, without affecting the final color and apply slow shutter speed under strong sunlight exposureCs. They also allow wider apertures, effectively decreasing the depth of field. The ND4 filter reduces the intensity by two degrees, the ND8 reduces by three degrees. the ND16 reduces by four degrees.the ND32 reduces by five degrees.