What Is Ketra? Lutron’s Natural Light Explained

Ketra is a line of light fixtures made by Lutron. What separates it from ordinary LED lighting is what is inside each fixture: three colored LEDs and one white LED, working together. That combination lets a single fixture produce a wide spectrum of color and color temperature, instead of the one fixed output a normal bulb is stuck with for its entire life.

Color temperature, in plain terms

Everyone understands color. Color temperature is the part that gets skipped, and it is the part that decides whether a room feels right.

Color temperature describes variations in the appearance of white light. High color temperature reads slightly bluish. Low color temperature reads slightly amber. Natural sunlight moves from low to high and back to low as the day progresses: amber at sunrise, cool and blue at midday, amber again in the evening.

Most light fixtures are locked at one point on that scale. You buy "cool white" or "warm white" and that is what the room gets at seven in the morning and eleven at night alike. Ketra fixtures can be warm, cool, and everything in between, and they can move across that range on a schedule.

Why your body cares about this

That daily cycle of changing light is called circadian rhythm, and it controls how the body releases the hormones that affect alertness during the day and quality of sleep at night. Lutron makes a controller that uses Ketra's range to follow that cycle indoors, so the light in the house tracks what the light outside is doing.

In practice that means a kitchen that is bright and cool at breakfast and warm and low by late evening, without anyone touching a switch. It is the difference between lighting that works around your day and lighting you have to work around.

CRI, and why colors look wrong under ordinary light

The other measure that matters is CRI, the Color Rendering Index. CRI measures how accurately a light source shows an object's true color compared to natural daylight. Typical lamps land somewhere between 50 and 80. Ketra fixtures are 90 CRI and above, which is excellent, and they hold that rating across their entire range of color temperatures. That consistency is rare and it is the hard part.

The difference is easiest to see rather than describe:

Color, not only white

Ketra fixtures can also produce colored light, which gives interior designers a wide palette of scenes to work with. Used with restraint it is a genuine design tool rather than a party trick, and it is recalled from the same keypads as everything else.

Where Ketra earns its place in a house

Kitchens, because food and stone counters look completely different under accurate light. Rooms with art, where a low CRI fixture flattens exactly what the piece was bought for. Dressing rooms and closets, where matching clothes under bad light is a daily annoyance. And great rooms with large glass, where daylight sits right next to the fixtures and makes any mismatch obvious.

That last one matters in Denver. Homes here are built around light and views, with big west and south-facing windows. When the daylight coming through the glass is that good, mediocre interior lighting has nowhere to hide, and the contrast between the two is visible all afternoon.

Ketra runs on your Lutron system

Ketra is not a bulb you buy and screw in. The fixtures are controlled through a Lutron system, RadioRA 3 or HomeWorks, which means they live on the same keypads, scenes and schedules as the rest of the lighting and the motorized shades. One button sets the light level, the color temperature and the shade position together.

It also means Ketra is specified and commissioned by a Lutron dealer rather than bought off a shelf. The fixtures have to be laid out against the room, and the daily color temperature curve has to be tuned once the house is furnished.

Talk to us about Ketra

Electronic Services and Concierge is a Lutron Diamond Dealer in Lakewood, Colorado. We design, install and commission Ketra lighting for homes across the Denver metro area, Summit County and Vail.

Call 720-532-0199 to talk about what Ketra would do in your rooms.