HMI Par

Overview

The HMI Par is a type of film lighting fixture that combines an HMI discharge lamp (HMI = Hydrargyrum Medium-arc Iodide) with a parabolic reflector (PAR = Parabolic Aluminized Reflector). Like all HMI lamps, it produces light not via a filament, but through an arc between two electrodes in a quartz envelope. This results in the typical characteristics of HMI technology: daylight-like color temperature and significantly higher luminous efficacy per watt compared to incandescent (Tungsten) light.

Unlike the HMI Fresnel, which is adjusted from spot to flood using a movable lamp-reflector carriage, the Par works with interchangeable spreader lenses. The reflector focuses the light into an intense, far-reaching beam; the lens placed in front then widens this cone. Consequently, for the same power output, the Par delivers higher center intensity and greater throw than a comparable Fresnel, but without its continuous spot/flood adjustment.

Technical Characteristics

• Light Type: Daylight, depending on the manufacturer and lamp age, in the range of approximately 5600–6000 K.
• Operation: Requires an external ballast; electronic ballasts enable flicker-free operation and, in some cases, limited dimming.
• Startup: The lamp must be ignited (strike) and takes a few minutes to reach stable color temperature and full brightness; a hot lamp cannot be reignited immediately (restrike pause).
• Light Shaping: Instead of a zoom, various lenses are changed tool-free – staggered sets from narrow spot through medium and wide to super-wide flood are common. An inserted frost/Fresnel lens produces softer light.
• Models: Available in common HMI power classes (e.g., 575 W, 1.2 kW, 2.5 kW, 4 kW, 6 kW, 12 kW, 18 kW). Well-known model series include ARRI Arrisun and LTM Cinepar, among others.

On-Set Usage

The HMI Par is the standard tool when a lot of daylight-colored light is needed over a long distance. Typical uses include lighting exterior scenes to fill against the sun, simulating sunlight through windows, and shooting through diffusion frames (e.g., frames with fabric). Since the daylight color temperature mixes directly with sunlight and skylight, it can be used to supplement outdoor light without conversion gels.

Due to its narrow, long-throw beam, the narrow spot is often used for distant positions or for shooting through, while wide and super-wide lenses cover broader areas closer to the subject – each with a corresponding loss in center intensity. Practical considerations include the space required for the separate ballast, the cable connection between the head and ballast, and the warm-up and restrike times when relocating.