HMI Lighting for High-Speed Photographic Applications
High-speed photography requires high levels of illumination for good color quality and color retention. As the frames/sec increases, so does the intensity of light required. The HMI is a medium-arc, high-efficiency, cool, high-intensity discharge lamp capable of maintaining a 5600-K color temperature at high levels of illumination, with a dramatically reduced level of emitted infrared (IR) radiation. A new ballast is described that takes full advantage of the HMI lamp and eliminates problems, particularly flicker, associated with traditional magnetic ballasts. This power source, installed between the utility power (AC) or battery pack (DC) and the HMI lamp, provides modified square waves of regulated current. The lamp operates at cooler internal temperatures and maintains a uniform 5600-K color temperature, extending its useful life from 500 to approximately 2160 hr. Color temperature reduction due to aging decreases from 1 to 0.3 K/hr. Film shot at 10,000 frames/sec exhibited no flicker or color shift.
- Print ISSN
- 0036-1682
- Published
- 1989-12
- Content type
- Original Research
- DOI
- 10.5594/J03943