The Heliopan 37mm Orange Filter is a basic contrast filter, primarily for use with black and white film, that strongly darkens blues and greens, increases overall contrast, and is often used for outdoor photography to emphasize contrast and shadows. It is also well-suited for decreasing atmospheric haze when photographing with long lenses and to smooth skin tones for portraiture. There is an approximate 4x filter factor with this filter, requiring an increase of 2 stops for normal exposure. For increased cloud effects, darkens sky and lightens clouds.