Phot r p series neutral density filters have several uses and offer the possibility to achieve otherwise unachievable results nd filters appear grey and reduce the amount of light reaching the film they have no effect on colour balance they have four main uses 1 to enable slow shutter speeds to be used especially with high speed films to record movement in subjects such as waterfalls clouds or cars 2 to decrease depth of field by allowing wider apertures to be used which helps sepa