Often it is necessary or desirable to balance the light intensity in one part of a scene with another. This is especially true in situations where you don't have total light control, as in bright contrasty landscapes. Exposing for the foreground will produce a washed-out, over-exposed sky while exposing for the sky will leave the foreground dark and under-exposed. Hitech Graduated Neutral Density (ND) Filter allows the transition to be blended into the scene, often imperceptibly. The hard edge is recommended for normal and longer lenses.