4000W HMI

Overview

"4000W HMI" does not refer to a single fixture, but rather a power class of daylight-balanced fixtures utilizing a 4-kilowatt HMI lamp. HMI stands for Hydrargyrum Medium-arc Iodide – a metal halide gas-discharge lamp that generates light via an arc between two electrodes, rather than a filament. Unlike Tungsten sources, HMIs inherently provide daylight color temperature and are significantly more efficient, producing a light output from a 4kW lamp suitable for exterior and large interior shots.

The 4kW class is a common "workhorse" standard on set: large enough to simulate windows, fill shadows, or push through diffusion, but without the logistical overhead of 6kW, 12kW, or 18kW heads. The lamp is housed within the fixture head; it must be operated via a separate electronic ballast, which ignites and stabilizes the arc.

Types and Common Models

The 4kW lamp is used in various head types:

• Fresnel – with a stepped lens for a cleanly focusable, controllable spot/flood beam (e.g., ARRI Compact 4000W / D40, FilmGear, Came-TV, and Cinelight Fresnels).
• PAR – lensless with interchangeable lenses (lens kits) for high throw and brightness (e.g., ARRI ARRISUN 40/25).
• MAX / lensless – a focusable reflector fixture with high output (e.g., ARRI M40).

Many 4kW heads are designed as dual-wattage, accepting either a 2500W or a 4000W lamp, which is often reflected in the model name (e.g., "40/25").

Technical Specifications (Example: Osram HMI 4000 W/SE/XS)

Values refer to the single-ended Osram/Sylvania lamp (model 54321); other manufacturers and designs may vary.

HMI lamps are also manufactured as double-ended (e.g., Osram HMI 4000 W/DXS). The daylight characteristic is specified by manufacturers in the range of approximately 5600–6000 K.

Set Usage

The 4kW HMI always requires a compatible electronic ballast, typically configured as a 2500/4000W ballast. Modern electronic ballasts operate flicker-free and offer switchable high-frequency modes (e.g., 300 Hz or 1000 Hz) for slow-motion shooting. HMIs are only dimmed to a limited extent – typically down to about 50% – as heavy dimming affects color temperature and arc stability; for finer adjustments, diffusion, nets (scrims), or distance are usually employed.

Practical notes: HMI lamps ignite with high voltage and require a cool-down period after being switched off before they can be reignited (unless equipped with hot-restart). Due to UV emission and the lamp's burst pressure, the protective front glass is a safety feature and must not be removed during operation.