Full Spectrum Light Bulbs
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FULL-SPECTRUM LIGHTING: FACT OR FICTION?
You’ve probably heard the following about full-spectrum lighting:
- It simulates natural outdoor light.
- It portrays true colors.
- It reduces glare, fatigue, and eye strain.
- It illuminates details and color.
- It makes work environments more productive.
- It brings the benefits and beauty of the outdoors to a building’s interior space.
But do you know if these statements are accurate? There are strong associations between full-spectrum lighting and daylight or “natural” light and between full-spectrum lighting and health benefits - due in part to marketing efforts. In 2003, Lighting Research Center’s National Lighting Product Information Program (NLPIP) surveyed 250 lighting designers, electrical contractors, and facilities managers to gauge views and opinions on full-spectrum lighting. The respondents largely believed that full-spectrum lighting helped to improve mood, mental awareness, Seasonal Affective Disorder, and color perception. Some believed that full-spectrum lighting improved dental health, sleep quality, and vitamin D production as well. According to some claims, full-spectrum lighting should provide these benefits to the end-user. But do these lamps really perform as they’re marketed? Are they truly superior? Here is what this type of lighting actually offers and what it doesn’t.
1. There are many different definitions of full-spectrum lighting.
When coupled with lighting, the term “full spectrum” implies that a light source offers even, uninterrupted spectral energy distribution (SED) (also called spectral power distribution [SPD]) without the peaks and valleys associated with most discharge light sources (such as fluorescents, metal halides, etc.).
The Lighting Research Center defines “full-spectrum” as an equal-energy lamp (a lamp that provides equal energy in all visible wavelengths), according to Peter Boyce, professor emeritus at the Lighting Research Center. He points out: “There is also an operational definition which says that a full-spectrum lamp has some energy in all visible wavelengths, has a correlated color temperature of at least 5000K, and some UV emission.”
Some maintain that UV radiation is an essential part of full-spectrum lighting; but full-spectrum lamps that reduce radiation in a small part of the visible spectrum (in an effort to improve visibility) have emerged, and these products also have the “full-spectrum” label.
According to Brian Liebel of AfterImage + Space (principal investigator for the U.S. Department of Energy in terms of spectrally enhanced lighting, and a research leader on increased brightness and visual-acuity benefits of higher color-temperature lighting), the technically correct definition for full-spectrum lighting is “any light source that contains lighting energy throughout the visible spectrum.” Liebel also shares a second definition that describes full-spectrum lighting as a term used by some manufacturers that claim their products provide a more even distribution of lighting throughout the visible spectrum, similar to the way light energy is distributed in daylight.
The problem here? There is no recognized definition of full-spectrum lighting. In many cases, lighting professionals indicate that the term is nothing more than a marketing tool being used to garner attention.
The only real full-spectrum source is the sun. There are some electric light sources that come pretty close but nothing available for commercial use that is truly full-spectrum. A more accurate term would be “fuller-spectrum”.
2. You may be able to purchase full-spectrum lamps without the "full-spectrum" label.
Within each color Kelvin, there are lamps with varying ranges in the color spectrum (indicated by the color rendering index [CRI], which ranges anywhere between 60 and 90). The high color-spectrum sources (80+) are considered full-spectrum by the lighting industry. If you opt for a 5000K lamp (that looks very blue/white) with a CRI of somewhere between 80 and 90, that’s ypically what is used to simulate natural light. Whether or not it has the ‘full-spectrum’ label depends on the manufacturer.
Full-spectrum lamps are frequently priced somewhere between 4- to 12-times higher than comparable lamps without the “full-spectrum” label. The increase in price is typically due to claims being made about the lamps: better visibility, enhanced color perception, improved health, and greater productivity.
In short: Full-spectrum lamps have a color temperature greater than 5000K and a CRI of over 90. Whether or not they’re labeled as “full-spectrum” depends on the manufacturer.
3. Many of the claimed benefits regarding full-spectrum lighting may not be true.
Energy efficiency. Although some full-spectrum lamps do claim to be energy efficient, full-spectrum lamps are usually not as energy efficient as comparable lamps without the “full-spectrum” label. They’re less energy efficient due to the heavier phosphors that are used. Full-spectrum fluorescent lamps are low-pressure, mercury-discharge lamps with a phosphor coating.
Health improvements. Most professionals agree that full-spectrum lamps don’t provide any health benefits beyond what most other electric light sources do. About health and full-spectrum lighting, the Lighting Research Center’s NLPIP report explains that short wavelength (blue) light is predominantly effective at regulating the human body’s circadian system; long wavelength (red) light seems to be inconsequential to the circadian system. So, to capitalize on affecting the circadian system and general health, a light source shouldn’t imitate a full spectrum, but should maximize short wavelengths. According to the report, even if a full-spectrum light source includes short wavelength light in its spectrum, it won’t ensure proper circadian regulation since the proper intensity, timing, and duration of light exposure are all equally important as well. In fact, in most published reports with claims of health improvements, those were conducted or funded by the manufacturers of full-spectrum lighting. However, there are numerous independent studies performed by reputable research institutions showing no health benefits.
Lighting quality. Where visual performance or worker satisfaction is important, it’s important to think about the quality of the light. With full-spectrum lighting, you’re just talking about color quality; there are a whole bunch of other lighting quality issues such as visual comfort, glare, uniformity, and contrast ratios that are also an important part of the lighting conversation. Just because you buy a full-spectrum lamp doesn’t mean it’s going to solve all of your lighting issues.
4. Full-spectrum lamps do offer a few advantages in some situations.
There are some instances where full-spectrum lamps outshine other fluorescent sources. The lamps provide very good color-rendering, an increase in brightness for the same luminance, and slightly better visual acuity for the same luminance. But whether or not these benefits will actually affect your building’s occupants or tenants depends on the tasks they’re performing. If color identification is part of the job (such as in graphic arts, printing applications, or matching paints or textiles) full-spectrum lamps will ensure good color discrimination. But, any white lamp with a high CRI could be expected to facilitate color-matching just as well by definition.
In research that’s been documented over the last 5 to 8 years, it’s been discovered that higher color Kelvin (like 5000K) helps improve visual acuity and accuracy. So, in places where you’re doing color evaluation, or speed or accuracy of the workers is important, you may wish to consider a 5000K source.
Keep these four truths in mind when you consider full-spectrum; but, remember, it’s difficult to accurately describe a lighting technology on paper. The only way you can really know is to experience it. Go to a lighting showroom and ask to see a demonstration of 3000K; 3500K; 5000K; etc., and lamps with low color-rendering and high color-rendering. That way you can make a better decision about which full-spectrum or fuller-spectrum light source you want to install.