Phot r p series nd4 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 nd4 represents how much light enters the lens in terms of a fraction so this nd4 filter lets 14 of the amount of light in they have four main uses 1 to enable slow shutter speeds to be used especially with high speed films to record movement in subj