Have you ever noticed how “white” lights seem to vary in color? Some light bulbs seem yellowish, others almost blue; some seem to have no color at all but give an unpleasant “cold” light that’s very unflattering. This is because every light bulb (or LED) has a built-in “temperature.” Light temperatures are measured in degrees, on the “Kelvin scale.”
Museums, art galleries, clothing and jewelry stores pay particular attention to light temperature, because lighting is reflected by the items on display. Even a few degrees Kelvin, one way or another, totally changes how colors appear to the human eye. It’s important to render the color of an art masterpiece, or a sweater, the way its creator intended. Colors look very different depending on the light source.
Color temperatures over 5000 Kelvin are called “cool colors” (bluish), while lower color temperatures (2700–3000 Kelvin) are called “warm colors” (yellowish). Low color temperatures will feel warmer while higher color temperatures will feel cooler. A warmer (lower color temperature) light is often used in public areas to promote relaxation, while a cooler (higher color temperature) light is used to enhance concentration, for example in schools and offices.
The most popular traditional light bulbs or fluorescent lights give “warm” light, which tends to be more flattering to people and plants. As we transition to LED’s (Light Emitting Diodes) for energy efficiency, we have to pay more attention to light temperature, because manufacturing “warm” or flattering LED’s is simply more expensive than “cool” LED’s.
LED manufacturers have closely-guarded “recipes”, precisely layering different materials onto a wafer, which is then baked in an oven. The organic nature of LED production means that yields are not totally predictable. Just like a batch of chocolate chip cookies, wafers do not come out of the oven precisely uniform. This is where “binning” comes in. After baking, each LED is “binned” or sorted based on color, intensity, and other different characteristics. This means that specific LED colors might be more plentiful than others, and thus less costly.
This is why cheap LED fixtures give off such an unpleasant, unflattering, “dead” bluish light; the kind you’d expect in a morgue or a factory. If you want “warm,” flattering light in your home or landscape, you have to seek out LED fixtures labeled 2700 Kelvin, or “daylight.” Even then, LED’s vary in longevity and brightness. You get what you pay for, as in most things.
When we design landscape lighting, we have to pay attention to what is being lit when we choose the light temperature of fixtures. Sometimes 3000 Kelvin is more flattering; for instance when lighting evergreens with blue-toned foliage like juniper and blue spruce. But for most scenes, 2700 most closely resembles natural sunlight and best brings out the true color of the subject. Warm-toned wood decks and hardscapes, colorful blooms and, of course, people, tend to look best in 2700 Kelvin light.
Most of all, we have to avoid mixing light sources that obviously don’t match each other. That calls for carefully chosen light temperatures, as well as good quality LED’s that won’t change color or brightness over time. We want our “light paintings” (that’s what we call the lit scenes in landscapes) to look perfect for years from now.
We’re all being forced by the government to replace standard light bulbs with energy-efficient LED replacement bulbs. Most replacement bulbs are labeled with the Kelvin temperature, so you can pick the right one for you. New light fixtures with built-in LED’s tend to be 4000 Kelvin or higher; very unflattering but very bright. Cheap, short-lived solar landscape lights give the worst light, and don’t last very long. If you want more pleasant, flattering lights that stand the test of time, you’ll have to be very picky about new fixtures, and not just buy the cheapest thing. It’s harder to find quality light fixtures, but well worth the trouble if you want beautiful surroundings.
Steve Boehme is a landscape designer/installer specializing in landscape “makeovers.” “Let’s Grow” is published weekly; column archives are on the “Garden Advice” page at www.goodseedfarm.com. For more information is available at www.goodseedfarm.com or call GoodSeed Farm Landscapes at (937) 587-7021.