It seems there might be some confusion here. HMI typically stands for Human-Machine Interface in the context of industrial automation. It doesn't directly relate to lights.

However, if you're referring to lights associated with HMI technology in film and photography, that's a different story.

HMI lights are a type of lighting commonly used in film, television, and photography. They are powerful and efficient lighting sources that produce daylight-balanced light, which closely matches natural sunlight. HMI lights work by passing an electric current through a special gas-filled bulb, typically a metal halide arc lamp. When the current flows through the gas, it generates an electric arc, which produces intense light across the visible spectrum, including blue and ultraviolet wavelengths.

HMI lights offer several advantages over traditional tungsten lights, including higher efficiency, lower heat output, and a more consistent color temperature. They are often used in outdoor or daylight shooting scenarios where natural sunlight is not available or needs to be supplemented. Additionally, they are commonly used in studio settings where precise control over color temperature and light intensity is required.

In summary, HMI lights work by passing an electric current through a gas-filled bulb to produce intense daylight-balanced light suitable for film, television, and photography.