The B+W #13 Green (061) 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 3x filter factor with this filter, requiring an increase of 1.6 stops for normal exposure. B+W filters are constructed from high quality Schott glass for increased optical clarity and color fidelity. They feature a brass filter ring for durability as well as jamming prevention. 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. Constructed from high quality Schott glass for optical clarity. Brass filter ring helps to prevent jamming and provides additional strength. PRODUCT HIGHLIGHTS #13 Filter for General B&W Contrast Rugged Black Brass Filter Ring High Quality Schott Glass Type: Green Size: 58mm Grade: 13 Filter Factor: 3 (1.6 stop) Effect: Lightens greens and foliage, subtly darkens skies Construction; Schott glass