Graduated Filter
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Or "Gradated" Filter. A filter that is not uniformly dense, but that gradually changes its density across the filter’s field.
A Graduated neutral density filter is clear from one edge to approximately the middle of the filter, then gradually increase in density towards the opposite edge.
Colored graduated filters gradually change color density across the filter’s field.
Graduated filters, are used to balance the light of a scene with overly bright highlights.
