The Leica E39 Orange Filter is a basic 39mm contrast filter, primarily for use for black and white photography. This orange filter noticeably darkens skies, helps to cut through haze, and improves overall contrast. When compared to a yellow filter, an orange filter creates a greater separation between clouds and sky and further lightens yellows and reds within the scene.
The effect of this filter is quite powerful. It darkens violet and blue very strongly, green strongly, it even darkens yellow-green a bit. Landscape- and architectural photographs have an increased, virtually “graphic” contrast, clouds in the sky already look dramatic. Because skin tones are strongly lightened in relation to the green tones of plants, this is a favored filter for nude photography outdoors, because it raises the contrast between the lighter bodies and darker landscapes