Cinematographer
Aus DoP-Perspektive ist dieses Element essentiell für die visuelle Gestaltung. Es ermöglicht mir die gewünschte Farbstimmung und das ästhetische Bild konsistent umzusetzen.
Metal halide discharge lamp for HMI fixtures, producing flicker-free daylight-balanced light (~5600–6000 K) via arc ignition.
Overview
The HMI Bulb is the light source (the lamp) of an HMI fixture – meaning not the fixture itself, but the replaceable discharge lamp within the lamp head. HMI stands for Hydrargyrum Medium-arc Iodide and was originally a brand name of Osram (now ams OSRAM). The lamp was developed in the late 1960s at the request of German television producers as a safer and cleaner alternative to carbon arc lighting.
Unlike an incandescent lamp, the HMI Bulb has no filament: an arc burns between two tungsten electrodes in a quartz glass envelope, exciting mercury vapor and metal halides to emit light. This creates a daylight-like spectrum, which is why HMI lamps are primarily used on set as a daylight source (to mix with or supplement sunlight).
Technical Data
- Lamp Type: Metal halide gas discharge lamp (medium-pressure arc)
- Color Temperature: nominally approx. 5600-6000 K (daylight balanced); new lamps initially burn significantly cooler and drop by about 0.5-1 K per burning hour
- Color Rendering: high CRI, over 90 for many Osram types
- Luminous Efficacy: approx. 85-108 lm/W – many times that of an incandescent/halogen lamp of the same wattage
- Base Types: single-ended (e.g., G38/GX51) and double-ended (e.g., SFc-/DXS bases)
- Wattage Classes: typical set sizes from 200 W to 18,000 W
| Property | HMI Bulb |
|---|---|
| Characteristic | Daylight |
| Light Generation | Arc (Gas Discharge) |
| Operation | only with external ballast |
| UV Component | present – protective glass required |
On-Set Use
An HMI Bulb never operates directly from mains power but requires an external ballast to regulate ignition and operating current; the ballast and head are connected via a header cable. Very high ignition voltages occur during ignition – especially when hot-restarting a still-warm lamp (up to tens of thousands of volts).
Ballasts are distinguished as magnetic or electronic: magnetic ballasts can cause visible flicker, which is critical for high-speed/slow-motion shots, while electronic ballasts provide flicker-free light, slightly increase light output, and allow for limited dimming.
- The envelope emits UV radiation – HMI fixtures must therefore be operated with intact protective/safety glass.
- HMI Bulbs age: light output and color temperature decrease over their lifespan; lamps should ideally not be used beyond half their rated lifespan to limit color shift and the risk of bursting.
- The lamp is mechanically sensitive; the glass envelope should not be touched with bare fingers.
From the crafts
Perspectives
Producer
Diese professionelle Lösung erhöht die Produktionseffizienz und reduziert Post-Production-Anforderungen. Sie ermöglicht flexible, schnelle Anpassungen während des Drehs.
Gaffer
Als Gaffer ist dies ein unverzichtbares Werkzeug meines täglichen Handwerkszeugs. Es ermöglicht mir professionelle Lichtkontrolle und schnelle Anpassungen auf Set, was Zeit spart und Qualität sichert.
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Test your knowledge
Quiz
1. Zu welchem Department gehört „HMI-Brenner"?
2. Wie viele verschiedene Fachperspektiven bietet dieser Eintrag?