Conversion bulbs are available for some metal halide ballasts. The bulb looks like a metal halide, but produces a light spectrum similar to a HP sodium lamp. The 360-watt conversion bulb works on a 400-watt metal halide ballast, and the 940-watt bulb works on a 1000-watt metal halide ballast. Although not as bright as regular HP sodium lamps, conversion bulbs are more economical than buying two complete systems.
