High Intensity Discharge Light Bulbs
High-intensity discharge bulbs, also referred to as HID bulbs, produce light by arcing electricity between electrodes inside of a gas and metal salt infused housing. They are much more efficient
than both fluorescent and incandescent bulbs because they produce much more visible light per amount of electricity used. They are the predominant choice for streets, highways and parking
garages where abundant low-cost light is required for thousands of hours with little or no maintenance. HID bulbs start with an arc of light that is initially created by the gas in the bulb. The reaction
is then carried on by heating the metal salts. The end result of this reaction is plasma that produces very intense light with very little power consumption.
The four primary types of HID bulb are; metal-halide, mercury vapor, and high and low-pressure sodium. The differences between the varieties centers on the color and intensity of the light
produced by the chemical composition of the bulb. Metal-halide lamps are preferred where color accuracy is more important. Metal-halide lamps can produce a neutral white light that is suitable
for automotive headlights and video production. Sodium vapor bulbs can be either low pressure or high pressure. Low pressure sodium vapor bulbs are very efficient, and produce the amber color we
are all familiar with from street lights. High pressure sodium produces a more neutral white light. Mercury vapor bulbs produce light with a distinct blue tint to it. In many countries, including the
USA, mercury lighting is being phased out in favor of the more efficient types of HID bulbs. Mercury vapor light is still used in special applications such as photolithography which requires a strong
ultraviolet light (UV) source.