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 to reflect ultraviolet light. In effect, females are removing the ultraviolet signal that initiates male sexual behavior, resulting in the abrupt halt of male sexual behavior. Female White Cabbage Butterflies take advantage of the personal butterfly ultraviolet communication system to also reject males by removing an ultraviolet reflectance signal. Some butterfly species use ultraviolet light as a method of signaling their sex. For example, in the species "Eurema lisa", males possess the structural requirements necessary to reflect ultraviolet light discussed previously, but females lack the ultraviolet light reflecting ridges. In both sexes of this species, a flutter response, or the