Advancing the effective use of light for society and the environment.

Monday, October 6, 2003

Lighting Answers clarifies many of the claimed benefits of full-spectrum lighting

Manufacturers of full-spectrum light sources have capitalized on the lamp’s spectral qualities by advertising a multitude of benefits that come with exposure to this type of “natural” light. But what does “natural” mean, and do the lamps perform as marketed? The latest publication from the National Lighting Product Information Program (NLPIP), Lighting Answers: Full-Spectrum Light Sources, examines the attributes of full-spectrum lamps, including product and performance characteristics, product definitions, consumer perceptions, and the validity of manufacturers’ claims.

Full-spectrum lamps are often priced four to 12 times higher than comparable lamps without the full-spectrum label because of the benefits manufacturers claim they provide, such as better visibility, enhanced color perception, improved health, and greater productivity. In this study, NLPIP delved into the marketing and benefits aspects of full-spectrum light sources to assess the product’s strengths and weaknesses.

Impacts of marketing, effects on vision and health

NLPIP surveyed 250 lighting specifiers, electrical contractors, and facilities managers to gauge their perceptions on the impact of full-spectrum light sources. Overall, the respondents believed that full-spectrum lighting has a positive effect on the majority of claimed benefits, including color perception, visual clarity, mood, and productivity. “The marketing message from manufacturers of full-spectrum light sources appears to be getting through to its intended audience,” said LRC Director Mark Rea, who led the research team for the report.

The product and performance evaluation conducted by NLPIP sheds light on a number of these marketing claims. Among the findings is that full-spectrum lighting offers no significant health benefits. “Full-spectrum light sources cannot necessarily offer better visual performance and certainly cannot improve your health,” said Rea.

Researchers define visual performance as the speed and accuracy of processing achromatic information, such as black print on white paper. Because of the relatively high light levels found in most schools and offices, visual performance is unaffected by the spectral power distribution of the light source, meaning that full-spectrum lamps will not help people see any better in these environments. However, people will perceive full-spectrum lighting as being brighter because of the lamp’s high correlated color temperature and color rendering properties.

Indeed, full-spectrum lamps offer excellent color rendering, said Rea. Visual tasks requiring good color discrimination, such as graphic arts work, will benefit from full-spectrum lighting.

Recent research into lighting’s effect on health has shown that solar light/dark cycles strongly influence people’s daily activities, including the sleep/wake cycle. Short wavelength (blue) light has been shown to be most effective at regulating the circadian system. Full-spectrum lamps emit a wide variety of wavelength radiations, which means that the relative power of the short wavelengths decreases for the same amount of total light output. “Given the other radiations included in a full-spectrum lamp, the effect of the short wavelength is diluted for the purpose of circadian regulation,” said Rea. He added that light levels are also a necessary consideration in garnering the benefits of full-spectrum lighting. “Intensity as well as spectrum is important.”

Lighting from full-spectrum lamps also does not enhance the treatment of seasonal affective disorder because any white light source will be effective if used at the recommended exposure levels for treatment, the report states.

Exposure to full-spectrum lighting may produce some positive psychological benefits, although no biophysical evidence exists to explain the improved mood observed in some people. Rea noted that the placebo effect associated with natural light could be a powerful partner for full-spectrum light sources because of their positive association with daylight.

Definition for full-spectrum light sources

In addition to evaluating product capabilities, the Lighting Answers report offers a proposed definition for full-spectrum light sources, which had not existed in the past. Various manufacturers have different ideas about what a full-spectrum light source is and why it yields the claimed benefits. For example, some say that ultraviolet radiation is a necessary ingredient in full-spectrum light. Recently, however, several lighting products have emerged that reduce radiation in a small part of the visible spectrum in an effort to improve visibility. These products also are called full-spectrum.

“With each manufacturer making up its own definition of full-spectrum lighting, consumers have no way to know exactly what they are getting, let alone what benefits to actually expect,” said Rea. The definition proposed in the report quantifies the extent to which a given light source deviates from a full-spectrum light source.

For more information, click here to read Lighting Answers: Full-Spectrum Light Sources.

About the LRC

The Lighting Research Center (LRC) is part of Rensselaer Polytechnic Institute and is the leading university-based research center devoted to lighting. Founded in 1988, the Lighting Research Center has built an international reputation as a trusted and reliable source for objective information about lighting technologies, applications, and products. Its mission is to advance the effective use of light and create a positive legacy of change for society and the environment

© 2003 Rensselaer Polytechnic Institute, Troy, NY 12180 USA.

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