Full-spectrum light
From Wikipedia, the free encyclopedia
Full-spectrum light is light that covers the electromagnetic spectrum from infrared through near-ultraviolet, or all wavelengths that are useful to plant or animal life; in particular, sunlight is considered full spectrum, even though the solar spectral distribution reaching Earth changes with time of day, latitude, and atmospheric conditions.
"Full-spectrum" is not a technical term when applied to an electrical light bulb but rather a marketing term implying that the product emulates natural light.[1]
Products marketed as "full-spectrum" may produce light throughout the entire spectrum, but actually do not produce an even spectral distribution, and may not even differ substantially from lights not marketed as "full-spectrum".[1][2]
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[edit] Measurement
Color temperature and Color Rendering Index (CRI) are the standards for measuring light. There is no technical definition of "full-spectrum" so it cannot be measured. To compare "full-spectrum" sources requires direct comparison of spectral distributions.
A cube of carbon will radiate light of varying spectral power distribution (SPD) as it is heated. At 0 K, it is pure black, while at about 5,000 K to 5,500 K, it appears similar to noon daylight.
[edit] Use in art and in color matching
Full-spectrum fluorescent lamps are used in the art studio by artists who paint pictures on canvas when they paint at night or inside (ideally, during the day the art studio should have north sunlight, but many artists don't have access to north sunlight so they use full-spectrum lamps instead) in order to make sure that the colors they are using appear in their natural hue as they will appear when the painting is displayed in a home or in an art gallery.
Full-spectrum lamps are also used by color scientists or color matchers in paint stores to match colors at night or inside when they don't have access to north sunlight.
[edit] Use in gardening
Gardening under lights keeps plants blooming almost year-round, for a wintertime harvest. Some plants grow better when given more of a certain color light, due to the mechanism of photosynthesis.
[edit] Use in seasonal affective disorder
In recent years, full-spectrum lighting has been used in the treatment of seasonal affective disorder (SAD) through the use of "light boxes" that mimic natural sunlight, which may not be available in some areas during the winter months. Light is an environmental stimulus for regulating circadian cycles.
Lightbox therapy, otherwise known as phototherapy, is a recognized modality for depression (such as SAD). Depending on the quality of the light, it is estimated that 10,000 lux is needed for effective treatment. Not all light boxes are the same.
[edit] Independent verification
The non-profit Lighting Research Center, a group of utility companies, experts and government agencies, established the National Lighting Product Information Program (NLPIP) to provide objective information about the effectiveness of different lighting systems. According to the NLPIP, full-spectrum light does not provide any improved benefits over similar light systems.[3] [4]
A Cornell study casts doubt on the use of full-spectrum lighting in restaurants to promote sales.[5]
The National Research Council of Canada Institute for Research in Construction, a Canadian government research and development agency, has published several scientific articles about full-spectrum lighting, collected on their web page. The authors of these papers also have concluded that full-spectrum lighting (~5000 K, CRI>90) does not confer any benefits on performance, mood, or health compared to typical cool-white fluorescent lighting.[6][7]
[edit] See also
[edit] References
- ^ a b "Full-spectrum Light Sources". Lighting Answers 7 (5). September. http://www.lrc.rpi.edu/programs/NLPIP/lightingAnswers/fullSpectrum/abstract.asp. Retrieved 2007-11-01.
- ^ Galidakis, I.N.. "The Double Amici Prism Hand-Held Spectroscope". http://ioannis.virtualcomposer2000.com/spectroscope/amici.html#fullspectrum. Retrieved 2007-11-01.
- ^ Full-Spectrum Light Sources - Light Research Center
- ^ Sylvania's Statement on FS Lighting with US Gov links Sylvania PDF
- ^ "Cornell study finds full-spectrum lighting has no effect on restaurant sales". Cornell Chronicle. 2007-09-14. http://www.news.cornell.edu/stories/Sept07/restaurants.lights.RN.html. Retrieved 2007-11-01.
- ^ McColl, S.L.; Veitch, J.A. "Full-spectrum fluorescent lighting: a review of its effects on physiology and health," Psychological Medicine, 31, (6), August, pp. 949-964, 2001 [(NRCC-43097)
- ^ Veitch, J.A.; McColl, S.L. "A Critical examination of perceptual and cognitive effects attributed to full-spectrum fluorescent lighting," Ergonomics, 44, (3), February, pp. 255-279, February 01, 2001 (NRCC-42840).
