hydrargyrum medium-arc iodide lamp
HMI lamp

Hydrargyrum medium-arc iodide lamps, designed initially for use in film, are now seen commonly on stage.

He shot the film on Kodak Vision Expression 500T film stock generally with two Panavision cameras, using lighting ranging from relatively dim candles to bright hydrargyrum medium-arc iodide lamps.

The gasses in an HMI lamp are under pressure, which increases with temperature.

In addition to these concerns, HMI lamps have been known to explode violently at the end of their lifetime or if stressed enough.

HMI lamps can reach ignition voltages of up to 70,000 V when striking hot, and are considered very dangerous if miswired.

This is accomplished by replacing the lamp assembly on the back of the Source 4 with an HMI lamp head.

HMI lamps are approximately the same color temperature as the sun, and as with most other mercury-based high intensity discharge lamps, generate ultra-violet light.

For HMI lamps, flicker can be avoided by the use of electronic ballasts that cycle at frequencies thousands of times faster than the mains frequency.

An HMI lamp uses mercury vapour mixed with metal halides in a quartz-glass envelope, with two tungsten electrodes of medium arc separation.

Within the last ten years, a lot of research has gone into making HMI lamps smaller because of their use in moving light fixtures such as those manufactured by Vari-Lite, Martin, Robe, and Highend.

Unlike tungsten-halogen lamps where the 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.

For the visual part of the composition a large mobile sculpture was built from optical lenses by Carl Zeiss, mirrors and color filters, which are spotlighted by 12 HMI lamps to create spectral light reflections in the planetariums projection dome.

As a result, HMI lamps should not be used past half their rated lifetime, and care should be taken with larger lamps when striking (turning on the lamp), as a lamp is most likely to explode within the first five minutes of striking.