The HMI 575-watt metal-halide discharge lamp: Measurements and predicted effects of intensity ripple using sinusoidal lamp excitation

A description is given of measurements of the light intensity ripple characteristics shown by 575 watt metal halide discharge lamp, when excited from a sinusoidal power source at various frequencies in the range 50Hz to 2kHz. Operating conditions which reduce motion picture film exposure variations to acceptable limits in the presence of this ripple component are discussed. The observed magnitude of the intensity ripple component in light from the lamp depends on the frequency of the alternating lamp supply, the waveform of the current passing through the lamp, the power dissipated in the lamp, and the spectral characteristics of the equipment used for the measurement of the intensity variations.