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A brief overview describing types of LED color-tunable products along with associated characteristics, advantages, and issues.
U.S. Department of Energy

This is the text-alternative version of Understanding LED Color-Tunable Products.

Color-tunable luminaires are different from normal luminaires in that instead of being one constant color they can change in color. We have three basic flavors on the market. One is called dim-to-warm, which starts out at a normal whitish color-- like a 3000k or 4000k. And then as you dim it down it warms up very much like halogen. It dims down smoothly. It can dim down to warm color temperatures. And it saves a lot of energy compared to incandescent.

One of the disadvantages when you have controls that are dimming too warm, if you want to reduce the light level, you're also changing the color temperature. You're warming it up as you dim down. So for example, you can't have your color at 3500k and then dim it down to a lower light level and still keep it at 3500k. The number one application is any place where you might want a whiter light during the day and then in the evening you want to dim down to lower light levels and have that reddish warm color come out-- restaurants, hotel lobbies, where skin tones look very good and some interiors look very, very pleasant.

Second kind is a white-tuning luminaire, which means you can tune from a cool color of white, which is a little bit bluish, down to a warm color of white, which is more yellowish. White-tunable products have a wide range of applications. For example, retail. In the winter time I'm selling ski boots and ski pants. I want a cool color of light to suggest that you're on the slopes in the snow enjoying the blue sky. So that's a high color temperature. But in the summertime, you want to be selling swimsuits. And if you're selling swimsuits, you might want to suggest the warm beach by using a warmer color of light. So with just a quick flip of a controller, you can shift from that very cool to very warm.

A third application that is being discussed is being able to tune the color of light for circadian rhythms. We have an internal body clock that responds to both the intensity of light and the color of light. And whiter, bluer kinds of light in high intensities may tend to wake us up and lower, warmer colors of light may tend to calm us down and make us more relaxed and ready to sleep. In the near future, there may be some guidelines for providing color-changing luminaires to help support the circadian system.

And then the third kind of color-tunable luminaires is called full-color-tunable. Those are luminaires that allow you to go from a white of different color temperatures all the way out to a bright red or a bright purple or anything in between. Full-color-tunable products are really for places where you want to completely change the mood at any given time. You want an office space where you want workers to be working under high light levels of maybe a cooler color in the morning, warmer color and lower light levels in the afternoon, and then in the evening you want to have a cocktail party. So you want to turn that office space into a place with bright purple or spots of red and blue. You don't have to have duplicate numbers of luminaires. You can have one luminaire do it all.