If you've ever walked past a movie being filmed at night, you most likely shielded or averted your eyes from the amount of light being directed at the scene until they adjusted. Even then, it was probably startlingly bright.
Motion picture film takes a
lot of light in order to properly expose. Unlike with still photographic film, you can't just lengthen the
exposure time in order to capture the requisite amount of
photons - you're bound by your medium. Twenty-four
frames of film per second will pass through your camera no matter what you do (barring fast-motion filming, perhaps) and you have less than 1/24 of a second worth of light to expose each frame. You have to transport the film, after all, which eats up some of the time.
In order to compensate when it gets dark, or if you're shooting indoors, or essentially anywhere that isn't saturated with bright sunlight, especially in the early days of film, there was only one answer. Light the scene, and light it bright.
The new Edison electric lights weren't powerful enough. In 1896, two German brothers who had immigrated to the U.S.A. formed a company. Their names were John H. Kliegl and Anton Kliegl, and the Kliegl Bros. Universal Electric Stage Lighting Company, in 1911, began to produce tube-shaped carbon arc lamps. These lamps could be used indoors, and were enclosed to allow the bright white light of a carbon arc to be directed (via lensing and reflectors placed around the front) at a particular location. Originally used as the 'spotlight' familiar to theatergoers everywhere, carbon arc lights took the place of the burning limelight famous in stage lore. They were soon adapted for film use, however, as their brilliance and close color resemblance to bright daylight began to allow the filming of 'daytime' scenes both indoors and at night.
Originally, these new lights were known as Kliegl-lights for their makers. This was shortened quickly to 'Klieg light', and this term eventually came to cover any carbon-arc stage or film light. The true Klieg light swiftly acquired a fresnel lens and positionable reflector panels around the front, which is the shape most easiy recognized today, as well as a sealed lamp. Eventually, incandescent bulbs were made that were powerful enough to produce the light levels required of a Klieg, and in 1933 incandescent bulb Klieg lights were available.
The Kliegl Brothers' company continued in business until the 1990s, although they passed away around the middle of the century.