The Hitech 85mm Standard Neutral Density 0.9 Filter is a professional quality 4 stop (16x) ND filter. Hitech Neutral Density Filters extend the control of exposure parameters & are used in both colour & black & white photography to reduce the intensity of visible light. They are extremely useful in pictorial photography when shooting maximum apertures in bright light. Since ND filters uniformly reduce light of all wavelengths, there is no effect on the colour rendition. These 84x 84mm filters fit in the Cokin P filter holder & are manufactured from the highest quality optical grade polyester resin.