Full-Spectrum Lighting: Nothing But the Truth

11/02/2005 |

Four things you probably don’t know – but should – about full-spectrum lighting

You know what the manufacturers declare 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 fact, in 2003, the Troy, NY-based Lighting Research Center’s National Lighting Product Information Program (NLPIP) surveyed 250 lighting specifiers, 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? On these pages, we report the full-spectrum facts. Find out 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 5,000K, 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, principal, 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), Emeryville, CA, the technically correct definition for full-spectrum lighting is “any light source that contains lighting energy throughout the visible spectrum.” But he 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. “Technically, all white light sources are ‘full-spectrum’ sources, whereas the marketing behind full-spectrum lighting claims improvements beyond typical white light sources,” he explains.

It’s clear why facilities professionals are confused: It seems as if almost everyone has a different idea about what a full-spectrum lighting source is. Some manufacturers have been known to create their own definitions of full-spectrum lighting based upon their products; consequently, facilities professionals have assumed things that may not be true about full-spectrum lighting.

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,” says Stefan Graf, principal, Illuminart, Ypsilanti, MI. “There are some electric light sources that come pretty close - used in film and video - but nothing available for commercial use that is truly full-spectrum. It should be called ‘fuller-spectrum.’ ”

Still befuddled? Graf provides a helpful analogy: In the audio spectrum, there are bass ranges, treble ranges, mid-ranges, and all sorts of different frequencies in between. “A full-spectrum sound system would produce all of the frequencies - from very low to very high frequencies - evenly across the speaker system. A full-spectrum lighting system, like the sun, would equally deliver all of the frequencies of light ... fluorescent light sources that attempt to do that still have peaks and valleys. There are certain frequencies that are missing and certain frequencies that are more prevalent.” (These frequencies are measured in nanometers; to be full-spectrum, a lamp would have to deliver all frequencies - from 380 nanometers up to 760 nanometers.)

2. You may be able to purchase full-spectrum lamps without the "full-spectrum" label.
In accordance with what a full-spectrum lighting system should deliver (all of the frequencies of light from 380 nanometers up to 760 nanometers), Graf says that lamp manufacturers should offer SED/SPD charts for their fluorescent light sources so that you can examine the frequencies they produce. With an SED/SPD chart, you’ll be able to see that lamps without the “full-spectrum” label may produce frequencies just as evenly as a lamp with the “full-spectrum” label.

“The other part of the full-spectrum equation (besides nanometers and SED/SPD charts) is the color Kelvin,” notes Graf. Color Kelvin (which is color temperature, noted in degrees Kelvin) indicates how warm or cool a light source is. When talking fluorescent lamps, there are five basic color Kelvins common in commercial buildings, ranging from very warm to very cool. Warm light/warm Kelvin (3,000K) fluorescent looks similar to incandescent light. As color Kelvins get higher, they look bluer. “All of these different color Kelvins produce what you consider ‘white light.’ But it’s like different shades of white - it’s like picking paints for a wall. You can find 50 different shades of white paint for the wall, but once you paint the wall, it looks like white paint - it doesn’t look pink or purple or green or yellow,” explains Graf. Manufacturers should also be able to provide color Kelvin data so that you can compare and decide which is best for your application.

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). According to Graf, the high color-spectrum sources (80+) are considered full-spectrum by the lighting industry. “So, if you opt for a 5,000K lamp (that looks very blue/white) with a CRI of somewhere between 80 and 90, that’s typically what is used to simulate natural light. Whether or not it has the ‘full-spectrum’ label depends on the manufacturer,” he explains.

As Graf reveals, there are some manufacturers that sell only full-spectrum lamps (5,000K lamps). “Because that’s primarily all they do and it’s a specialized market, they can charge more money. But often you can find the same lamp with the same color Kelvin and same color spectrum for about a third of the cost if you do some research.”

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. “[These lamps are] much more expensive in first cost and slightly more expensive in operating cost,” explains Boyce.

So, to simplify: Full-spectrum lamps have a color temperature greater than 5,000K 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, Liebel says that 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,” he explains. (Full-spectrum fluorescent lamps are low-pressure, mercury-discharge lamps with a phosphor coating.)

In a report from the Ottawa, ON-based National Research Council of Canada’s Institute for Research in Construction, Jennifer Veitch indicates that full-spectrum lamps also produce less light per unit of electrical energy (which means more lamps are required to maintain the same level of illumination as a cool-white installation). According to Veitch, maintenance costs don’t necessarily favor full-spectrum lights, either. Several reports imply that lamp life in some installations may be shorter for full-spectrum lamps than for other lamp types, although the reasons for this are unclear. And, depending on the lamp, facilities professionals must replace full-spectrum fluorescent lamps often enough to maintain the ultraviolet component, or use a special luminaire with separate UV lamps (which are replaced more often than the white-light lamps) to preserve the spectral composition.

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.

“The only reports that I have read with claims of health improvements were conducted or funded by the manufacturers of full-spectrum lighting, whereas there are numerous independent studies performed by reputable research institutions showing no health benefits,” says Liebel.

Lighting quality. “In any place where visual performance or worker satisfaction is important, it’s important to think about the quality of the light. With full-spectrum lighting, we’re just talking about color quality; there are a whole bunch of other lighting quality issues (like visual comfort, glare, uniformity, 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 your] lighting problems,” explains Graf.

4. Full-spectrum lamps do offer a few advantages in some situations.
There are some instances where full-spectrum lamps outshine other fluorescent sources. Boyce indicates that 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, as Veitch’s report discloses, any white lamp with a high CRI could be expected to facilitate color-matching just as well by definition.

Liebel agrees: “Most full-spectrum light sources have high color temperatures, which have been demonstrated to increase brightness perception and visual acuity. However, there are other ‘traditional’ fluorescent light sources that accomplish the same high color temperature without having the ‘full-spectrum’ label.”

According to Graf, “In research that’s been documented in the last 3 to 5 years, [it’s been discovered] that higher color Kelvin (like 5,000K) 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 5,000K source.”

Keep these four truths in mind when you consider full-spectrum lighting for your facilities; but, remember, it’s difficult to accurately describe a lighting technology on paper. “The only way you can really know is to experience it,” says Graf. “Go to a lighting showroom and ask to see a demonstration of 3,000K; 3,500K; 5,000K; etc., and lamps with low color-rendering and high color-rendering. You can make a better decision about which full-spectrum or fuller-spectrum light source you want to put in your building that way.”

Leah B. Garris (leah.garris@buildings.com) is associate editor at Buildings magazine.

Clearing Up Confusion ...
The term full-spectrum lighting (explained in this article) and the term light and human health shouldn’t be confused. They are two different subjects (as explained below by Terry McGowan, executive director, Lighting Research Office, Cleveland):

Light and Human Health
This is a new area of medical research, which seeks to determine the effects of both electric (artificial) illumination and daylighting on human health. The research indicates, for example, that people (and many other living things) need bright days and dark nights to maintain healthy circadian rhythms and proper levels of certain hormones such as melatonin. Researchers are looking at light intensity, duration, timing, body coverage, and color as some of the variables, and they are particularly interested in how electric lighting systems might be designed to provide healthier interior environments. (See Buildings magazine’s March 2004 issue for more info or access at [www.buildings.com/Articles/detail.asp?ArticleID=1781].)

Full-Spectrum Lighting
Some years ago, the term “full-spectrum lighting” began to appear in lighting articles to describe certain proprietary fluorescent and incandescent lamps that had out-of-the-ordinary color characteristics. While a definition of what “full-spectrum” actually is has never been settled upon by any of the standardizing or technical organizations in the lighting industry, the term continues to be used to suggest that there are certain benefits, perhaps even including better health, if lamps so designated are used. Whether those benefits are worth the typically higher cost of the lamps, or go beyond simply changing the appearance of people and things seen under the light of “full-spectrum” lamps, is controversial. The bottom line: Check carefully any claims made by promoters of full-spectrum lighting. Be sure the claimed benefits are real.


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