Once the preserve of high specification premium cars High Intensity Discharge (HID) lamps are fast becoming standard fit in mainstream vehicles. HID lamps have a 'blue' hue which separates them from the regular tungsten-halogen filament lamps, which tend to have a yellow hue. Despite HID lamps having a greater amount of light output per amount of electricity energy input, along with a much improved luminous efficiency that transforms a greater amount of energy into visible light rather than heat, HID lamps are still mainly used in dip-beam operations. However, they are used for dip and main beams in some applications. Where HID lamps are used in dip-beam operations, traditional tungsten-halogen lamps are used for main-beam. Even though a common name for most HID lamps is xenon headlamps, they are frequently metal halide lamps that contain xenon gas. Metal halide lamps are frequently used in street lamps and for floodlighting of sports pitches, warehouses and compounds. The xenon gas is used to allow the lamp to produce an initial amount of light immediately after power-up, in order to accelerate the (much longer) runup time of the lamp. Other types of technologies include mercury vapour, ceramic metal halide and sodium vapour. All automobile applications of HID lamps use xenon, but not all of them use this gas for the whole functioning time.
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