Ultraviolet photography sensor will pick up reflected infrared radiation as well as ultraviolet, which may obscure the details that would be resolved by ultraviolet alone. Most types of glass will allow longwave UV to pass, but absorb all the other UV wavelengths, usually from about 350 nm and below. For UV photography it is necessary to use specially developed lenses having elements made from fused quartz or quartz and fluorite. Lenses based purely on quartz show a distinct focus shift between visible and UV light, whereas the fluorite/quartz lenses can be fully corrected between visible and ultraviolet light without focus shift. Examples
Ultraviolet communication in butterflies rapid opening and closing of the wings, is performed when a male approaches another butterfly; yet, males copulate with females who perform this behavior, while retreating from males who perform the flutter response. By showing that male and female wings are similar in appearance except for UV reflectance and an approaching male is exposed to ultraviolet reflection of a male's wings during a flutter response, as well as ruling out temporal differences in the flutter behavior as a cause for sex recognition, Ronald Rutowski concluded that ultraviolet light was being used as an indicator of the male sex. However, in