Full-spectrum light

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Full-spectrum light is light that covers the electromagnetic spectrum from infrared to 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.

Contents

"Full-spectrum" is not a technical term when applied to an electrical light bulb. Rather, it implies that the product emulates some important quality of natural light. [1]

Products marketed as "full-spectrum" may produce light throughout the entire visible spectrum, but without producing an even spectral distribution. Some may not differ substantially from lights not marketed as "full-spectrum". [1] [2]

Color of daylight and a blackbody, compared CIE illuminants D and blackbody small.gif
Color of daylight and a blackbody, compared

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 distribution.

Color emitted by a black body on a linear scale from 800 kelvins to 12200 kelvins Color temperature black body 800-12200K.svg
Color emitted by a black body on a linear scale from 800 kelvins to 12200 kelvins

The emission spectrum of a light source varies depending on the light generating mechanism. Thermal sources such as incandescent bulbs produce electromagnetic radiation over a broad and continuous range of wavelengths, including infrared and ultraviolet. A black body radiator is the idealized version of a thermal source. As the temperature of a black body radiator increases, the shape of its spectral distribution changes with more energy emitted at shorter (bluer) wavelengths.

Sources that rely on fluorescence have a different emission spectrum shape than do thermal sources. Some wavelengths will be produced with greater amplitude than others. Fluorescent sources used for lighting, such as fluorescent lamps, white light-emitting diodes, and metal halide lamps are intended to produce light at all wavelengths, but the distribution is different from thermal sources and so colors will appear different under these forms of lighting than under daylight; some colors may match under one light source that don't appear the same under another, a phenomenon called metamerism.

Where light sources use an electric discharge through low pressure gas, the light spectrum may be quite discontinuous, with some wavelengths of light missing or at very low amplitude. Such light sources have a strong tint, such as low pressure sodium lamps, or neon lamps. These lamps are used more for their color effects than for general illumination. Some scientific instruments use discharge tubes to produce light that has only a few wavelengths in it, a so-called "line spectrum". A laser is a single-wavelength source, which would produce light of a very pure color.

Use in art and in color matching

Ideally, during the day, an art studio (in the northern hemisphere) should be lit with northern sunlight, because it is considered more neutral and diffused than the direct, "yellowish" quality of southern sunlight. Since many artists' studios lack north-facing windows, full-spectrum lamps are sometimes used to approximate such light. Full-spectrum fluorescent lamps are also used by color scientists, color matchers in paint stores and quilters and others working with fabrics or yarn when working under inadequate lighting conditions to assist in achieving the correct hues as they will later appear in daylight or under gallery lighting.

Use in aquariums

Full spectrum lighting is used both for tropical and marine fish as well as many other aquatic pets. The use of full spectrum lighting assists aquarium plants to grow and aids in the health of the fish and the tank as a whole. While plants have adapted to the reception of real sunlight, full spectrum light bulbs often mimic the emphasis of wavelengths of sunlight enough that plants are stimulated to grow. Full spectrum lighting also enhances the natural coloration of fish, plants and other aquatic elements in an aquarium, which are often discolored by artificial lights. Full spectrum lighting is typically used more in fresh-water aquariums since marine or coral-reef aquariums often require intensely blue light.

Use in gardening

Gardening under lights keeps plants blooming almost year-round, for a wintertime harvest. Grow lights are specifically intended to support plant growth, although with varying degrees of success and energy efficiency. Some plants grow better when given more of a certain color light, due to the mechanism of photosynthesis. Specifically more blue wavelengths enhance vegetative growth and development, while the addition of increasing amounts of red light enhances budding, flowering and fruiting.

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). It is also the primary treatment for circadian rhythm sleep disorders. 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, and some produce only blue or green light.

A reduction in exposure to sunlight during winter months and the shift in times or sunrise and sunset can affect a person's Circadian rhythm/internal clock, serotonin levels and melatonin levels. [3] Symptoms of SAD may be more pronounced in women (75% of SAD cases), in younger adults (18-30), those with depression or a family history of depression, and it is also more common in those who live more than 30 degrees north or south of the equator. [4]

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) in the USA 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. [5] [6]

A Cornell University study reached mixed conclusions on the use of full-spectrum lighting in restaurants to promote sales. [7]

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. [8] [9]

See also

Related Research Articles

<span class="mw-page-title-main">Color temperature</span> Property of light sources related to black-body radiation

Color temperature is a parameter describing the color of a visible light source by comparing it to the color of light emitted by an idealized opaque, non-reflective body. The temperature of the ideal emitter that matches the color most closely is defined as the color temperature of the original visible light source. The color temperature scale describes only the color of light emitted by a light source, which may actually be at a different temperature.

<span class="mw-page-title-main">Fluorescent lamp</span> Lamp using fluorescence to produce light

A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than an incandescent lamp, but is less efficient than most LED lamps. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. For comparison, the luminous efficiency of an incandescent bulb may only be 16 lumens per watt.

<span class="mw-page-title-main">Lighting</span> Deliberate use of light to achieve practical or aesthetic effects

Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylight. Daylighting is sometimes used as the main source of light during daytime in buildings. This can save energy in place of using artificial lighting, which represents a major component of energy consumption in buildings. Proper lighting can enhance task performance, improve the appearance of an area, or have positive psychological effects on occupants.

<span class="mw-page-title-main">Blacklight</span> Light fixture that emits long-wave ultraviolet light and very little visible light

A blacklight, also called a UV-A light, Wood's lamp, or ultraviolet light, is a lamp that emits long-wave (UV-A) ultraviolet light and very little visible light. One type of lamp has a violet filter material, either on the bulb or in a separate glass filter in the lamp housing, which blocks most visible light and allows through UV, so the lamp has a dim violet glow when operating. Blacklight lamps which have this filter have a lighting industry designation that includes the letters "BLB". This stands for "blacklight blue". A second type of lamp produces ultraviolet but does not have the filter material, so it produces more visible light and has a blue color when operating. These tubes are made for use in "bug zapper" insect traps, and are identified by the industry designation "BL". This stands for "blacklight".

<span class="mw-page-title-main">Photometry (optics)</span> Science of the measurement of visible light

Photometry is a branch of optics that deals with the measurement of light in terms of its perceived brightness to the human eye. It is concerned with quantifying the amount of light that is emitted, transmitted, or received by an object or a system.

<span class="mw-page-title-main">Sodium-vapor lamp</span> Type of electric gas-discharge lamp

A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength near 589 nm.

<span class="mw-page-title-main">High-intensity discharge lamp</span> Type of electric lamp/bulb

High-intensity discharge lamps are a type of electrical gas-discharge lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. This tube is filled with noble gas and often also contains suitable metal or metal salts. The noble gas enables the arc's initial strike. Once the arc is started, it heats and evaporates the metallic admixture. Its presence in the arc plasma greatly increases the intensity of visible light produced by the arc for a given power input, as the metals have many emission spectral lines in the visible part of the spectrum. High-intensity discharge lamps are a type of arc lamp.

<span class="mw-page-title-main">Mercury-vapor lamp</span> Light source using an electric arc through mercury vapor

A mercury-vapor lamp is a gas-discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger soda lime or borosilicate glass bulb. The outer bulb may be clear or coated with a phosphor; in either case, the outer bulb provides thermal insulation, protection from the ultraviolet radiation the light produces, and a convenient mounting for the fused quartz arc tube.

The lumen is the unit of luminous flux, a measure of the perceived power of visible light emitted by a source, in the International System of Units (SI). Luminous flux differs from power in that radiant flux includes all electromagnetic waves emitted, while luminous flux is weighted according to a model of the human eye's sensitivity to various wavelengths; this weighting is standardized by the CIE and ISO. One lux is one lumen per square metre.

<span class="mw-page-title-main">Marine aquarium</span> Salt water aquarium

A marine aquarium is an aquarium that keeps marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only (FO), fish only with live rock (FOWLR), and reef aquaria. Fish only tanks often showcase large or aggressive marine fish species and generally rely on mechanical and chemical filtration. FOWLR and reef tanks use live rock, a material composed of coral skeletons harboring beneficial nitrogen waste metabolizing bacteria, as a means of more natural biological filtration.

<span class="mw-page-title-main">Compact fluorescent lamp</span> Fluorescent lamps with folded tubes, often with built-in ballast

A compact fluorescent lamp (CFL), also called compact fluorescent light, energy-saving light and compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent light bulb; some types fit into light fixtures designed for incandescent bulbs. The lamps use a tube that is curved or folded to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp.

Actinism is the property of solar radiation that leads to the production of photochemical and photobiological effects. Actinism is derived from the Ancient Greek ἀκτίς, ἀκτῖνος. The word actinism is found, for example, in the terminology of imaging technology, medicine, and chemistry, and the concept of actinism is applied, for example, in chemical photography and X-ray imaging.

Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power, measured in lumens per watt in the International System of Units (SI). Depending on context, the power can be either the radiant flux of the source's output, or it can be the total power consumed by the source. Which sense of the term is intended must usually be inferred from the context, and is sometimes unclear. The former sense is sometimes called luminous efficacy of radiation, and the latter luminous efficacy of a light source or overall luminous efficacy.

<span class="mw-page-title-main">Growroom</span> Room for growing plants under controlled conditions

A growroom or growth chamber is a room of any size where plants are grown under controlled conditions. The reasons for utilizing a growroom are countless. Some seek to avoid the criminal repercussions of growing illicit cultivars, while others simply have no alternative to indoor growing. Plants can be grown with the use of grow lights, sunlight, or a combination of the two. Due to the heat generated by high power lamps, grow rooms will often become excessively hot relative to the temperature range ideal for plant growth, often necessitating the use of a supplemental ventilation fan.

<span class="mw-page-title-main">Artificial sunlight</span>

Artificial sunlight is the use of a light source to simulate sunlight where the unique characteristics of sunlight are needed, but where sufficient natural sunlight is unavailable or infeasible. A device used to simulate sunlight is a solar simulator.

<span class="mw-page-title-main">Grow light</span> Lighting to aid plant growth

A grow light is an electric light that can help plants grow. Grow lights either attempt to provide a light spectrum similar to that of the sun, or to provide a spectrum that is more tailored to the needs of the plants being cultivated. Outdoor conditions are mimicked with varying colour temperatures and spectral outputs from the grow light, as well as varying the intensity of the lamps. Depending on the type of plant being cultivated, the stage of cultivation, and the photoperiod required by the plants, specific ranges of spectrum, luminous efficacy and color temperature are desirable for use with specific plants and time periods.

<span class="mw-page-title-main">LED lamp</span> Electric light that produces light using LEDs

An LED lamp or LED light is an electric light that produces light using light-emitting diodes (LEDs). LED lamps are significantly more energy-efficient than equivalent incandescent lamps and fluorescent lamps. The most efficient commercially available LED lamps have efficiencies exceeding 200 lumens per watt (lm/W) and convert more than half the input power into light. Commercial LED lamps have a lifespan several times longer than both incandescent and fluorescent lamps.

Aquarium lighting describes any type of artificial lighting that is used to illuminate an aquarium. Some types of aquaria such as reef aquariums and planted aquariums require specialized high intensity lighting to support photosynthetic life within the tank.

<span class="mw-page-title-main">LED street light</span> Type of lighting fixture

An LED street light or road light is an integrated light-emitting diode (LED) light fixture that is used for street lighting.

<span class="mw-page-title-main">High-CRI LED lighting</span> LED lighting source

High-CRI LED lighting is a light-emitting diode (LED) lighting source that offers a high color rendering index (CRI).

References

  1. 1 2 "Full-spectrum Light Sources". Lighting Answers. Vol. 7, no. 5. March 2005 [September 2003]. Retrieved 2007-11-01.[ dead link ]
  2. ↑ Galidakis, I.N. "The Double Amici Prism Hand-Held Spectroscope" . Retrieved 2007-11-01.
  3. ↑ "Effects of reduced sunlight". LampsUSA. Retrieved 9 April 2018.
  4. ↑ "Who is most likely to develop SAD". Lamps USA. Retrieved 9 April 2018.
  5. ↑ Full-Spectrum Light Sources - Light Research Center [ dead link ]
  6. ↑ Sylvania's Statement on FS Lighting with US Gov links Archived 2006-12-01 at the Wayback Machine Sylvania PDF
  7. ↑ "Cornell study finds full-spectrum lighting has no effect on restaurant sales". Cornell Chronicle. 2007-09-14. Retrieved 2007-11-01.
  8. ↑ 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) Archived 2010-11-22 at the Wayback Machine
  9. ↑ 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) Archived 2011-06-11 at the Wayback Machine .
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