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 varies 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]

Color of daylight and a blackbody, compared.
Color of daylight and a blackbody, compared.

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[edit] Measurement

Color temperature and Color Rendering Index (CRI) are the standards for measuring light. In general, Kelvin temperature ratings of 5000 K or higher and CRI of 90 or higher denote a truer, full-spectrum light.

Color of a blackbody
Color of a blackbody

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. It is possible the phosphors used to mimic the natural light emit harmful ultraviolet radiation.[dubious – discuss]

[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] [5]

A Cornell study casts doubt on the use of full-spectrum lighting in restaurants to promote sales.[6]

[edit] See also

[edit] References

  1. ^ a b "Full-spectrum Light Sources", Lighting Answers, September. Retrieved on 2007-11-01. 
  2. ^ Galidakis, I.N.. The Double Amici Prism Hand-Held Spectroscope. Retrieved on 2007-11-01.
  3. ^ The Full-Spectrum Controversy - Apollo Light
  4. ^ Full-Spectrum Light Sources - Light Research Center
  5. ^ Sylvania's Statement on FS Lighting with US Gov links Sylvania PDF
  6. ^ "Cornell study finds full-spectrum lighting has no effect on restaurant sales", Cornell Chronicle, 2007-09-14. Retrieved on 2007-11-01.