This article about tunable-white lighting was originally published in tED Magazine. Reprinted with permission.

The color appearance of light sources—whether warm or neutral or cool—can have a big impact on how people and spaces are perceived. In applications like hospitality and high-end retail, the color temperature of a light source is a critical design decision. In the past, this choice was more or less fixed, and could only be changed by installing new lamps, color filters or independently controlled layers of warm and cool lamps.

In contrast, LED lighting can generate virtually any perceivable color as well as any shade of white light dynamically and with relative ease. This extraordinary capability of LED lighting has created a new category of tunable-white lighting and opened new applications and markets.

Approaches

Color-tunable LED products include full-color-tunable, dim-to-warm and tunable-white products. Full-color-tunable products can produce a range of saturated colors as well as white-light CCTs, though technical challenges for white-light emission, such as poor color rendering, generally limit application to entertainment lighting. Dim-to-warm products automatically reduce correlated color temperature (CCT) to achieve a warmer color appearance during dimming similar to the performance of a dimmed incandescent or halogen lamp. Tunable-white products, which may include a dim-to-warm feature, can be adjusted over a range of white-light CCTs.

Typically, tunable-white products enable adjustment through the combination of warm- and cool-CCT phosphor-coated LEDs, each separately dimmable. Relative dimming of these primaries can produce a range of CCTs, with color output following a linear path between the two points. Other colors may be added to increase flexibility of adjustment, allow some saturated colors, and produce a non-linear relationship between the primaries that follows the blackbody locus, enhancing the spectrum of available colors and color fidelity. Because dimming is the mechanism for changing CCT, the product’s overall intensity can be adjusted along with color. Though dimming increases efficiency, however, tunable-white LED products typically operate at a lower efficacy than their fixed-color counterparts.

“LED boards are basically an array of many miniature lights, and manufacturers can combine those different sources in various ratios to create differently colored white light sources,” says Bonnie Littman, President, USAI Lighting. “This could never be done before with previous lighting technologies—at least not well.”

Controls

Color control is typically implemented using 0-10V, DMX, DALI, Bluetooth or Wi-Fi (wireless), or a proprietary-protocol controller. David Ciccarelli, VP Dynamic Lighting, Acuity Brands Lighting, Inc., says controls are evolving along with LED product design to optimize color control.

“We have two choices to bring tunable-white to the mainstream from a controls perspective,” he says. “We can use ON/OFF/dimming systems and repurpose an intensity channel to deliver control of color temperature or other color attributes. We can design control systems that are ‘color aware” by including color attributes—e.g., CCT, Duv, hue—in addition to ON/OFF/dim. The first tunable-white systems in the mainstream will use the first approach, with a few limitations in that the interface/programming tools available to the designer will be left over from the ON/OFF/dim paradigm.”

For example, with an ON/OFF/dim system, there’s typically no way to implement a long theatrical-style intensity fade over a very long period of time, limiting availability for a multi-hour fade from one CCT to the next.

“Over time,” Ciccarelli adds, “mainstream systems will become color-aware—meaning the controller, network and luminaires will be speaking to each other in handles representing color. Therefore, the user interfaces will present the user with appropriate controls and selectors, allowing proper programming of the space to the intended application.”

Tunable-white lighting offers the ability to dramatically change how a space appears. Shown here are three different dim levels and color outputs for three applications: a healthcare environment (a), a kitchen (b) and an office space (c). Images courtesy of USAI Lighting.

Applications

Scott Roos, VP of Product Design, Juno Lighting Group, sees warm-to-dim products for residential and hospitality applications as the low-hanging fruit. “They are essentially replicating the expected and appreciated effects of longstanding incandescent and halogen technology,” he points out. “The technology can be relatively inexpensive and requires no additional design or commissioning time or expense, so there are really no barriers to widespread adoption. Tunable-white lighting, on the other hand, is opening up an entirely new frontier in lighting design and human health and productivity.”

Demand for tunable-white light is likely to be driven by aesthetics and productivity. In terms of aesthetics, tunable-white products can imitate the color appearance of popular light sources, customize new light sources, instantly change the look and feel of a space to adapt to different user preferences or space uses, and fine-tune color appearance appropriate to a new design or altered display or décor. Some products feature drivers that dynamically calibrate color appearance across products and maintain it over time.

“Tunable-white light can recreate the look and feel of other popular light sources such as metal halide without any of the maintenance headaches, and can also make possible the creation of custom light sources that you design,” Littman says. “These lighting options were unprecedented before LED technology. Fundamentally, tunable-white light makes lighting customizable and personalized. It gives users the flexibility to experiment with lighting within their environment in ways we were not able to do a decade ago.”

“Tunable-white will find applications most readily in retail and hospitality—in the places where lighting helps to sell goods and services,” Ciccarelli notes. “This can be done by helping to fine-tune the presentation of products for maximum visual presentation, or it can mean setting and transitioning the atmosphere of a gathering space to accomplish the goals of the designer and owners.”

Besides retailers, Littman points to art galleries and museums as another ideal application for tunable-white lighting. “The visual appearance of a product or a work of art can be greatly enhanced by this type of lighting.”

Roos says tunable-white lighting has many sales opportunities in applications driven by aesthetics, but the real frontier is lighting for human health and productivity—circadian lighting. There is a level of potential here that is transformative for the lighting industry, but the industry needs to be careful how it presents the benefits of circadian lighting. Traditional metrics such as CCT aren’t adequate to the task of predicting human circadian response, which is sensitive to spectral content, not actually CCT, of light. New metrics are being developed while our understanding of light’s relationship with circadian response continues to advance.

“In regards to selling circadian lighting, distributors should stick to educating customers on the basic facts without making specific health claims, and take extra care to do no harm,” Roos advises.

Final word

“Interest in bringing dynamic lighting into the mainstream, starting with tunable-white, is amazing right now,” Ciccarelli says. “We are finally at the point where the applications are understood well enough and the technology is accessible enough to make the 15-year-old dream finally come to fruition.”

“Everyone wants the latest technology without understanding the true value and benefit that a different type of lighting can provide them,” Littman says. “A distributor who is well informed with the latest products, uses and information will easily differentiate itself from competitors. It is critical for distributors to develop a network of reputable partners, manufacturers and resources that can help keep current with the human benefits of tunable-white light—what users are most interested in understanding today.”

Roos concludes, “While I can’t predict how quickly tunable-white technology will see wider adoption, I can confidently state that it is only a matter of time until it does. This is a unique opportunity for industry professionals to invest in education on this topic to position themselves as the experts who will be the ones to advance this emerging field in lighting.”

Craig DiLouie

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