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For almost a decade following the launch of the original ceramic metal halide lamps, the only notable improvements were based on mechanical refinements of the arc tube - for instance GE's 3-piece injection moulded arc tubes, and Osram's rounded Powerball arc tubes.
In 2005 Philips briefly introduced the Mastercolour Elite lamp, featuring an improved lamp chemistry that realised a significant improvement in colour rendering quality, efficacy and lifetime. However it was hampered by quality problems at the higher temperatures encountered when used in typical luminaires, and was quickly withdrawn from sale until the Elite technology had been fully refined and re-launched in 2007.
Meanwhile in 2006 Osram introduced its 'HCI Shoplight' lamps, delivering greatly superior colour rendering but without the other performance advantages. As the name implies, this quickly became successful in the lighting of retail spaces, where its colour rendering index of 95 was the best available in ceramic metal halide technology at the time. In addition to the high Ra, the all-important R9 red colour rendering index was increased from a negative value to 50. The effect was to make colours appear more natural and vibrant, to increase the apparent value of illuminated goods.
Whereas Philips achieved its higher colour rendering via an improved lamp chemistry that facilitated higher loading, the original Osram Shoplight lamps appear to achieve this simply via increased loading alone. Despite the 12,000 hour life claim, lumen depreciation of this original Shoplight lamp is very rapid, dropping below 70% at about 6000h. In later designs the lumen maintenance was improved considerably. |