The Neutral Density Hard Edge Master Kit contains the 3 most widely used ND densities – 0.3 (1 stop), 0.6 (2 stops) and 0.9 (3 stops) in both standrard and Hard Edge graduated versions. Neutral Density (or ND) filters produce a grey neutral effect and are used to reduce light in photography, enabling more control over exposure and depth of field without affecting color or contrast. hese filters are clear in the bottom half of the filter with a gradual transition to the ND effect in the top half. They are primarily used for light reduction in skylines of landscape shots. Graduated NDs are available in Soft Edge or Hard Edge varieties. Soft edge grads have a smooth transition from clear to ND. Hard edge grads have a more defined hard lined transition and are usuallye used for longer focal lengths. NDs are made in different densities according to the level of light reduction from 1/3 to as much as 10 stops of light.This 150mm filter kit is useable with Lee 150mm holder systems and similar holders. The graduated filters in this kit are 150mm wide but 170mm long to enable easy movement up and down in the holder. The kit is also available in 85mm, 100mm and 165mm sizes. Hitech filters are made from the highest quality 1.5mm optical resin.