The Graduated Neutral Density Kit from Cokin consists of three filters: 121L, 121S and 121M.
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. Cokin graduated gray ND filters are part clear, part neutral density. They allow the transition to be blended into the scene, often imperceptibly.
A Graduated Neutral Density filter is also used to create some unusual special effects such as capturing the "blur" of the rippling water of a waterfall or the swirling effect of city traffic. Since it allows the use of slower shutter speeds in bright light, it becomes possible to create these special effects that would normally not be possible to capture without the filter. And since it can also help to control your depth of field, it permits you to shoot at wider apertures. Ultimately, its value is in helping to prevent bright, overly washed out images shot in bright light.
Note! This kit does not include any adapter rings
Graduated Neutral Density Filter Kit for "A " Series
"A" Series Filter Holder