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. Graduated Neutral Density filters are part clear, part neutral density. They allow the transition to be blended into the scene, often imperceptibly.
Neutral Density factors: ND.6 (exposure adjustment = 2 stops, reduces ISO 1/4)
PLEASE NOTE: Filters can only be rented with a camera or lens.