Color Temperature and CRI in Landscape Lighting
Color temperature and color rendering decide whether a landscape looks natural at night or flat and washed out. When we started designing Sterling luminaires, getting both right was a requirement before we would put our name on anything. Here's how we approached it, and what to look for when you specify landscape lighting today.
Where we started
Our development began by matching a traditional 35W PAR36 lamp, which gave a more even spread across a landscape than the MR16 used in many fixtures. Once we matched it, we set out to improve it. We noticed that halogen sources created a hot spot near the fixture, and we didn't want to copy that look in LED. We wanted the best light source possible. That led us to Cree LED chips and optics designed to spread light evenly and farther than a standard PAR lamp, and in 2013 to our first dedicated LED luminaires.
Choosing a color temperature
Color temperature (CCT), measured in Kelvin, sets how warm or cool the light looks. Small changes matter outdoors. Too cool, and foliage and stone look stark and washed out. Too warm, and the light can overpower the subject you want to highlight. For most residential landscapes, 2700K and 3000K are the go-to choices: 2700K for a warm, traditional glow, and 3000K for slightly crisper light on greenery and stone. Most Sterling luminaires come in 2700K and 3000K, and the SL01 Up Light adds 5000K for moonlighting and special effects.
Why CRI and R9 matter
CCT tells you the color of the light. Color rendering tells you how true everything looks under it. CRI (Color Rendering Index) scores accuracy on a 100-point scale, and R9 measures saturated reds, which drive how warm wood, brick, flowers and skin tones look. TM-30 adds fidelity (Rf) and gamut (Rg) scores for a fuller picture. The SL01 Up Light is rated CRI 98+ with TM-30 Rf 94 and Rg 99, and the SL11 Archer Light is rated CRI 97+. For more on what low R9 looks like in the field, see why some landscape lights look pink.
Optics complete the picture
Good color only helps if the light lands where you want it. Sterling luminaires use a single-source LED with removable optics, so you can control beam spread and reduce glare while keeping color consistent across a project. Read more in our post on the precision advantage of LED optics.
Are you a lighting professional? Sign up for Sterling's contractor perks to get pro pricing and support on your next project.
About the author: Patrick Harders, LC, is co-founder and CEO of Sterling Lighting and founder and principal lighting designer of Dayloom. He has more than 25 years of experience designing and installing outdoor lighting, and he's one of only five landscape lighting designers in North America with Lighting Certified (LC) accreditation. His projects have won multiple international lighting awards, including landscape lighting winners in 2018 and 2021, and he leads design of Sterling's luminaires.
