Full-spectrum light is light that covers the

electromagnetic spectrum The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high ...

from

infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

to near-

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

, or all wavelengths that are useful to plant or animal life; in particular,

sunlight Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible spectrum, visible light perceptible to the human eye as well as invisible infrare ...

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 Electric light is an artificial light source powered by electricity. Electric Light may also refer to: * Light fixture, a decorative enclosure for an electric light source * ''Electric Light'' (album), a 2018 album by James Bay * Electric Light ( ...

. Rather, it implies that the product emulates some important quality of natural light. Products marketed as "full-spectrum" may produce light throughout the entire

visible spectrum The visible spectrum is the spectral band, band of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' (or simply light). The optica ...

, but without producing an even spectral distribution. Some may not differ substantially from lights not marketed as "full-spectrum".

Measurement

Color temperature 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 clos ...

and

Color Rendering Index A color rendering index (CRI) is a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with a natural or standard light source. ''Color rendering'', as defined by the Internat ...

(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. The

emission spectrum The emission spectrum of a chemical element or chemical compound is the Spectrum (physical sciences), spectrum of frequencies of electromagnetic radiation emitted due to electrons making a atomic electron transition, transition from a high energ ...

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 A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The radiation emitted by a black body in thermal equilibrium with its environment is ...

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 Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with colore ...

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 lamp 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, to produce ultraviolet and make a phosphor ...

s, white

light-emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corre ...

s, and

metal halide Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, s ...

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 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. Two varieties of such lamps exist: low pressure, and high pressure. Low-pressure sodium lamps ar ...

s, or

neon lamp A neon lamp (also neon glow lamp) is a miniature gas-discharge lamp. The lamp typically consists of a small glass capsule that contains a mixture of neon and other gases at a low pressure and two electrodes (an anode and a cathode). When suffi ...

s. 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 A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...

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'

studio A studio is a space set aside for creative work of any kind, including art, dance, music and theater. The word ''studio'' is derived from the , from , from ''studere'', meaning to study or zeal. Types Art The studio of any artist, esp ...

s lack north-facing windows, full-spectrum lamps are sometimes used to approximate such light. Full-spectrum

fluorescent lamps 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, to produce ultraviolet and make a phosphor ...

are also used by color scientists, color matchers in paint stores and

quilter Quilting is the process of joining a minimum of three layers of textile, fabric together either through stitching manually using a Sewing needle, needle and yarn, thread, or mechanically with a sewing machine or specialised longarm quilting ...

s 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 light 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 (typically a ...

s 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 Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

. 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 Seasonal affective disorder (SAD) is a mood disorder subset in which people who typically have normal mental health throughout most of the year exhibit depressive symptoms at the same time each year. It is commonly, but not always, associated w ...

(SAD) through the use of "light boxes" that mimic natural

, 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 Light therapy, also called phototherapy or bright light therapy is the exposure to direct sunlight or artificial light at controlled wavelengths in order to treat a variety of medical disorders, including seasonal affective disorder (SAD), circ ...

, is a recognized modality for depression (such as SAD). It is also the primary treatment for

circadian rhythm sleep disorder Circadian rhythm sleep disorders (CRSD), also known as circadian rhythm sleep–wake disorders (CRSWD), are a family of sleep disorders that affect the timing of sleep. CRSDs cause a persistent pattern of sleep/wake disturbances that arise eit ...

s. Depending on the quality of the light, it is estimated that 10,000

lux The lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, in the International System of Units (SI). It is equal to one lumen per square metre. In photometry, this is used as a measure of the irradiance, as perceived by ...

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. 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.

Independent verification

The non-profi
Lighting Research Center
a group of utility companies, experts and government agencies, established th
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. A

Cornell University Cornell University is a Private university, private Ivy League research university based in Ithaca, New York, United States. The university was co-founded by American philanthropist Ezra Cornell and historian and educator Andrew Dickson W ...

study reached mixed conclusions on the use of full-spectrum lighting in restaurants to promote sales. Th
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 thei

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.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, 200
(NRCC-42840)
{{Webarchive, url=https://web.archive.org/web/20110611200844/http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/nrcc42840/nrcc42840.pdf , date=2011-06-11 .

References

Lighting Ergonomics