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 (Light My Way) dealt with themes of anxiety and despair. Bono has described "Ultraviolet" as "an epic U2 song [but] the key of it left my voice in a conversational place and allowed a different kind of lyric writing." Producer Eno wrote that a combination of opposites within each song was a signature characteristic of "Achtung Baby" and that as part of that, "Ultraviolet" had a "helicopterish melancholy". In "Achtung Baby"s album package, "Ultraviolet" is presented next to a photograph of a crumbling Berlin building that has a Trabant parked in front of it. "Rolling Stone" noted that "Ultraviolet" was one of the