The Lee 100mm Neutral Density (ND) Grad Medium Filter Set contains three graduated resin filters (0.3, 0.6 & 0.9) that enable the photographer to adjust exposure (by 1, 2, & 3 stops) over part of the photograph without affecting colour balance. These ND Grads feature a medium transition from dark to light & are ideal to be used when elements of the scene protrude into the sky, be that the rooftops of buildings or the peaks of mountains. The nature of the transition between coated & uncoated areas of the filter means that the sky can be filtered with minimal impact on the land beneath it. Lee 100mm Filter Holder & Adapter Ring required.