The Tiffen 86mm Coarse Thread #13 (2) Green Filter is a basic contrast filter, primarily for use with black and white film. This green filter subtly darkens skies and lightens foliage. It is commonly associated for use with portraiture and attaining greater separation from skin tones and outdoor backgrounds. When compared to the #11 yellow-green filter, the #13 helps to lighten foliage and other green-colored subjects more. There is a 2x filter factor with this filter, requiring an increase of 1 stop for normal exposure. Tiffen filters are made using ColorCore technology, a process that involves laminating the filter substrate between 2 pieces of optical glass, grinding flat to a tolerance of 10,000th of an inch, and then mounting to precision metal rings. Green contrast filter for black and white film subtly darkens skies and lightens foliage. Suited for portraiture, this filter helps to separate skin tones from outdoor backgrounds. Tiffen filters are made using ColorCore technology, a process that involves laminating the filter substrate between 2 pieces of optical glass, grinding flat to a tolerance of 10,000th of an inch, and then mounting to precision metal rings.