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