![]() ![]() Volume 7 Issue 5
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September 2003 (revised March 2005)
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AbstractLighting Answers:Manufacturers of full-spectrum light sources have claimed a variety of benefits for their products, including better visibility, improved color rendering, better health, and greater productivity. Light sources promoted as full-spectrum can cost over ten times as much as nearly identical products that do not bear the full-spectrum claim. This report addresses questions about full-spectrum light sources: What are full-spectrum light sources? How valid are the claimed benefits? Are these products worth the extra cost? This report also proposes a convenient definition for full-spectrum light sources that can be used to quantify the extent to which a given light source deviates from a full-spectrum light source. This revision presents an improved calculation method for this new full-spectrum metric. IntroductionThe term full-spectrum was coined in the 1960s by photobiologist Dr. John Ott to describe electric light sources that simulate the visible and ultraviolet (UV) spectrum of natural light. There are now dozens of electric lighting products marketed as full-spectrum, some promising that they closely simulate daylight and can therefore provide benefits such as better visibility, improved health, and greater productivity. Among the claims:
Different companies have different ideas about what constitutes a full-spectrum light source, and what it is about full-spectrum light that yields the claimed benefits. Some insist that invisible-to-the-eye UV radiation is a necessary ingredient in full-spectrum light. Recently, several lighting products have emerged that reduce radiation in a small part of the visible spectrum in an effort to improve visibilityand these products are also called full-spectrum. Most full-spectrum light sources are marketed at a premium price over other light sources, and they generally produce fewer lumens per watt than comparable light sources. If valid, the benefits claimed for full-spectrum light sources would seem to be well worth the additional expense and the loss in efficacy. But with each manufacturer making up its own definition of full-spectrum lighting, consumers have no way to know exactly what they are getting or what benefits to actually expect. This Lighting Answers explores consumer perceptions about full-spectrum light sources and assesses the validity of various manufacturers' claims. This report also offers a definition of full-spectrum light sources.
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