The firecrest nd 18 is a solid 100x100mm neutral density nd filter with 6 stop reduction to allow the use of longer exposures and a wider aperture firecrest nd is a revolutionary new type of nd filter from formatt hitech rather than dyed resin firecrest is a carbon metallic coating used to create hyper neutral nds the filters are made from 2mm thick schott superwite glass and the multi coating is bonded in the middle to increase scratch resistance firecrest filters are neutral across al