To increase operating temperature, and hence vapor pressure, the arc tube close to the arc, typically an inner arc tube, is at least partially frosted. The outer bulb which surrounds the inner arc tube may also be frosted. The lamps have low color temperature and good color rendering index at high luminous output. The fill preferably includes metal halides of rare earth metals, and/or mercury. The outer bulb is preferably in the form of a reflector bulb.
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