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Once you use an HMI light, you'll have trouble going back to tungsten or florescent instruments. An HMI is a continuous light arc source (no filament) that emits light at a color temperature very close to that of daylight (5,600 K). It provides phenomenal light output with approximately four times the efficiency of tungsten-based lighting units. Related to its output efficiency, HMIs also run much cooler than tungsten units. The advantages of HMI are obvious when you use some of the latest lights from Bron Kobold USA and K5600.
Before we get to the specifics of the Bron Kobold and K5600 lights themselves, let's talk about how HMIs are different from other lights on the market.
Unlike tungsten lamps, which operate by passing an electrical current through a tungsten-based filament sealed in a glass enclosure filled with an inert gas, HMI lamps operate by creating an electrical arc between two tungsten-coated electrodes within the bulb, exciting the pressurized mercury vapor within the quartz-glass enclosure. Unlike traditional tungsten lights, HMIs use ballasts to ignite the arc and regulate electricity to the lamp head. With the increasing use of electronic ballasts rather than magnetic, HMI bulbs can provide a flicker-free light source appropriate to shooting at nearly any frame rate.
One problem with tungsten lamps is that much more energy is released as heat than as visible light. (Ninety to 95 percent of the bulb's energy is released as heat.) HMIs are more efficient, using far less power to deliver the same output. Watt for watt, HMI fixtures are two to four times brighter than their tungsten equivalent. Since HMIs have a greater output, you can use fewer of them to light the same area, resulting in a shorter setup/teardown time, fewer shadows, fewer cables to run and less power used overall.
Another difference between tungsten and HMI lamps is the color temperature of emitted light. Most tungsten lights produce light of 3,200 to 3,400 K, which is much warmer in color (less blue) than sunlight and HMI lamps. HMIs,...