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Hydrargyrum Medium-arc Iodide

Device that emits light via pressurized mercury vapor and metal halides. Ideal for imitating daylight, they keep relatively cool and have a very high light output. HMI light has a color temperature of around 5600K.
Hydrargyrum Medium-arc Iodide

Hydrargyrum medium-arc iodide, or HMI, is the trademark name of Osram's brand of metal-halide gas discharge medium arc-length lamp, made specifically for film and entertainment applications. Hydrargyrum comes from the Greek name for the element mercury.

An HMI lamp uses mercury vapour mixed with metal halides in a quartz-glass envelope, with two tungsten electrodes of medium arc separation. Unlike traditional lighting units using incandescent light bulbs, HMIs need electrical ballasts, which are separated from the head via a header cable, to limit current and supply the proper voltage. The lamp operates by creating an electrical arc between two electrodes within the bulb that excites the pressurized mercury vapour and metal halides, and provides very high light output with greater efficiency than incandescent lighting units. The efficiency advantage is near fourfold, with approximately 85–108 lumens per watt of electricity. Unlike regular incandescent halogen lamps where a halide gas is used to regenerate the filament and keep the evaporated tungsten from darkening the glass, the mercury vapour and the metal halides in HMI lamps are what emit the light. The high CRI and color temperature are due to the specific lamp chemistry.

Key Terms

brand metal halide gas discharge medium arc length lamp
entertainment applications
film
greek name
hmi
hydrargyrum
hydrargyrum medium arc iodide
metal halides
trademark name osram
units

Additional Resources

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Acronymn

HMI

Synonymns

Hydrargyrum Medium-arc Iodide
(none found)

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Sources & Credits

Last modified on May 27 2019
Content adapted from Wikipedia
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