A Klieg light is an intense carbon arc lamp especially used in filmmaking. It is named after inventor John Kliegl and his brother Anton Kliegl. They usually have a Fresnel lens with a spherical reflector or an ellipsoidal reflector with a lens train containing two plano-convex lenses or a single step lens.
The carbon-arc source was so bright that it allowed film directors to make "day" at night, which also heralded the era of blinding actors — a term coined as "Klieg eye".
In the early days of spotlights, the name "Klieg light" became synonymous with any ellipsoidal reflector spotlight (ERS), another carbon-arc source or any bright source. Initially developed for film, the Klieg light was adapted to an incandescent stage fixture in 1911.
Although not completely certain, the title of the first ellipsoidal reflector spotlight often goes to the 1933 Klieglight, which was first used to light an outdoor pageant in New York. Century Lighting introduced their Lekolite, developed by Levy & Kook, hence the "Leko", in the same year.
Kliegl Brothers Universal Electric Stage Lighting Company was founded in 1896 and grew to be the largest stage lighting company in the world. The company closed in the 1990s.