HMI

HMI stands for Hydrargyrum Medium Arc-length Iodide, and is a type of film lighting unit. HMI lights are much more efficient than tungsten lights and give out 4 to 5 times more light per watt of elecrical power. They produce light with a colour temperature of 5,600K which is equivalent to average daylight. One slight disadvantage with HMIs is that they need an elecrical ballast unit to operate and this can be quite bulky. You also need to be aware of the potential problem of flicker when using HMIs with a camera that is not running in sync with the mains power supply. This can be overcome by using a flicker free ballast.