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 UV reflecting scales are composed of raised longitudinal ridges and perpendicular cross ribs that connect the parallel running ridges, forming a grid. The ridges possess lamellae that run on top of and parallel to the ridges and microribs on its sides. The partial overlap of lamellae structures causes thin layer interference resulting in the reflection of light with a wavelength within the ultraviolet spectrum. The other ultraviolet signal in butterflies, absorbance, was determined to be governed by pigments called pterins. In wings containing this pigment, the wings are unable to reflect ultraviolet light as well as without the pigment because