Do HMIs ever incorporate a filament?

• A. Yes
• B. No
• C. Only in Some Models
• D. Only in High Wattage

Answer: (B)

HMIs are high-intensity discharge lamps that produce light from an electric arc inside a quartz arc tube, not from a heated filament. The light comes from the excited mercury vapor and metal halide compounds when a high voltage starts an arc between two electrodes, and then the ballast regulates the current to keep the arc going at the right intensity. A filament is a feature of incandescent lamps, where light is generated by heating a wire to incandescence. Because HMIs rely on a controlled arc for both light output and color stability, there is no filament inside them.