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Full spectrum light is a term used to describe light wavelengths that fall into the full range of electromagnetic radiation (EMR) frequencies. Known as the electromagnetic spectrum, this range includes wavelengths below long radio waves and above short gamma rays. This light range includes infrared radiation with wavelengths longer than that of visible light, and extending to ultraviolet with EMR wavelengths shorter than visible light. To put this into perspective, sunlight includes infrared and ultraviolet ranges, with light that is visible to the human eye being in-between. This is why enthusiasts of full spectrum lighting hope to obtain a light source that mimics natural sunlight.
This does not mean to say that light bulbs and home lighting accessories labeled as full spectrum truly deploy full spectrum lighting. In fact, the term has become somewhat of an industry catchphrase used to enhance the marketing appeal of such products, some of which may be considered broad spectrum at best. Other buzzwords soon followed.
For instance, many products list Kelvin temperature and a corresponding Color Rendering Index (CRI). Kelvin is a measurement of color temperature as it relates to the color hue of the light source, with zero being pure black and 5,000 units emulating the noonday sun. CRI is a scale assessment of how accurately an object appears true in color when compared to being viewed under a natural light source. Believing that they are savvy about full spectrum lighting, consumers often look to Kelvin temperature and CRI as indicators of quality.
However, since these specifications really don’t assure effectiveness, they are also advertising lures. In fact, many manufacturers only list them because so many consumers ask for this information. For that matter, many organizations dedicated to promoting research of full spectrum lighting ignore Kelvin and CRI completely in terms of study design and therapeutic applications.
Nonetheless, full spectrum lighting has gained considerable attention as a potential therapy for mood disorders related to seasonal depression. Commonly known by the generic term of Seasonal Affective Disorder (SAD), this condition is marked by disturbed sleep patterns and a general feeling of malaise. Since these symptoms appear to surface during winter, researchers and clinicians have concluded that they stem from a decreased exposure to natural sunlight. Numerous studies have found that phototherapy may improve mood by helping to regulate circadian rhythms and stimulate the production of the hormone melatonin. However, the research also suggests that this benefit is gained from exposure to short wavelength frequencies, or white to blue light, indicating that such lighting may not be necessary.
Artists and photographers also utilize full spectrum lighting, particularly when working at night. The simulation of natural light conditions helps to ensure that the creative work renders colors that appear as they would when being viewed in daylight. Employees of home improvement centers and hardware stores often mix paint under full spectrum fixtures to obtain an accurate color match. In addition, gardeners who force blooms or grow off-season plants indoors turn to full spectrum lighting to provide sufficient light that approximates natural sunlight.