The right lighting can lift your spirits and make you more relaxed and productive The right lighting can lift your spirits and make you more relaxed and productive. Any experienced designer will tell you that lighting is an essential ingredient when you're decorating a room — not the afterthought that many of us consider it. If you're tempted to spend more of your time picking out furnishings or puzzling over layouts, remember that LED lighting can completely transform a space — not just by brightening dark corners, but by affecting your emotions. "Light is a powerful thing," said Theo Richardson, the director of development at Rich Brilliant Willing, the Brooklyn-based design studio known for its striking LED fixtures, which he founded with Charles Brill and Alexander Williams. "The right light lifts the mood, inspires productivity and motivates us. At home, light enlivens the little things — our morning routines, or the moments we spend with friends." Most designers agree that you need more than one source of light in a room. Think layered illumination: Every room should have a mix of sports lighting, including overhead, accent and task lights. In the living room, for example, you might begin by hanging a decorative ceiling fixture near the center of the room, said Nathan Orsman, a port lighting designer based in New York City and Southampton. "Then we look toward the outer walls for downlighting that can gently wash the walls, curtains and art with warm, functional brightness," he said. This can be achieved with soffit or valance lighting, or even plug-in torchier floor lamps that bounce light off the ceiling. Depending on a room's layout, he said, accent lights could be used to highlight art, and table lamps could be placed beside seating to add another layer of light. And for extra ambience, he added, "a candle never hurt." The goal, he explained, is to create contrast between the light at the center of the room and around the perimeter, and the darker spaces in between: "Without the darker, quieter moments, everything is flat and boring. It's the subtle interplay between light and dark that creates appeal." One place where bright light is more important than ambience is the kitchen. Mr. Orsman suggested flooding the space by installing high-hats or recessed lights along the edge of the ceiling. If you have a kitchen island, consider hanging pendants overhead, he said, which will light the space without taking up room you might need to eat or prepare food. Also, you'll be able "to see your guests without having to look around a hanging light." And don't forget under-cabinet light: Running LED light strips on the bottom of your upper cabinets is the easiest way to create an evenly lighted counter space for food prep and cooking. If you have a north-facing room without direct sunlight, it will generally require a little more thought. Donna Mondi, an interior designer in Chicago, installed recessed fixtures along the perimeter of a north-facing living room to complement a central pendant that spread light horizontally throughout the space. But she didn't stop there: She also used table lamps to illuminate dark corners and a pair of sconces to draw attention to a special piece of art. For a dark bedroom, she used a similar strategy, combining a central chandelier with discrete up-lights in the corners of the room, bedside lamps for reading and a pair of sconces over the fireplace opposite the bed. "The worst option is a recessed fixture over the sink, as it casts shadows that are not flattering," Ms. Mondi said. Instead, she suggested, opt for wall-mounted sconces with 75-watt bulbs installed about 66 inches off the floor, which will help cast even illumination across your face. Another "great feature to add is industrial lighting at the cabinet base," she said, which creates "a very subtle glow" like a night light if you wake up in the middle of the night. To create a sense of intimacy and spalike luxury, consider installing a sculptural pendant lamp. Janey Butler, who runs Janey Butler Interiors, the interior design wing of the Llama Group in Cheshire, England, transformed a windowless bathroom into a dramatic space by hanging Ochre's Celestial Pebble Chandelier over the tub. "The light itself is a beautiful object that meets the eye on arrival to the room and provides focus to the free-standing bath," Ms. Butler said. She also used LED strip lighting, concealed behind floating shelves, to wash the chevron-patterned floor with a subtle glow. "When you have an empty and awkward corner, one trick of the trade is to transform that space with an oversized floor lamp," said Caitlin Murray, the founder and chief executive of Black Lacquer Design, in Los Angeles. "Look for a lamp that is complementary in finish and material to the surrounding space, and an otherwise lost corner instantly becomes an intentional, polished part of the overall room design." To brighten up the space next to a desk in a bachelor's living room, Ms. Murray chose the Detrick Floor Lamp, from Arteriors, in an earthy finish with a gray-green shade. "It did the double duties of providing added light to his work space while also being a statement accent piece," she said. "It was important to find something in tone and texture that both complemented the overall design and provided enough of a contrast to the surrounding neutrals to really make a visual impact." Don't Overdo the Overheads "Over the years, we've found that one of the biggest mistakes is made with overhead commercial lighting," said Robert Highsmith, a principal at Workstead, the Brooklyn design firm he founded with his wife, Stefanie Brechbuehler, and fellow Rhode Island School of Design alum Ryan Mahoney almost a decade ago. "Often it can be excessive, generating spots and unwanted shadows." For that reason, Workstead advises residential clients not to use recessed overhead lighting. Instead, Mr. Highsmith recommends hanging a large pendant fixture or a chandelier in common areas. In the kitchen, he suggested using globe fixtures, "for even lighting" that leaves counter surfaces free. For living rooms, he said, try subtle lighting sources like wall sconces and floor lamps, and in dining rooms, "a sculptural centerpiece above a table provides depth, while accent lighting amplifies warmth." Put dimmers on all of your lights: "Workstead prefers a more analog approach that allows you to manually adjust lighting to respond to changes in natural light, seasons and so forth," Mr. Highsmith said, noting that the easiest way to adjust the light in a room is by putting a dimmer on each fixture, rather than replacing a wall switch with a dimmer that adjusts all the lights at once. In the bedroom, he suggested using a bedside light with both a dimmer and a movable shade. Workstead designed the Orbit sconce, for example, to be adjustable in both ways, with a dimmer and a swiveling reflector that allows the light to be directed or blocked. "We feel like the more flexibility, the better," he said. Don't Forget the Details "Whenever you use a shade — whether it's on a lamp, a sconce or a chandelier — use frosted or soft-white bulbs to eliminate the shadows and hot spots created by shade clips," said Paloma Contreras, an interior designer in Houston. And be sure those shades are on straight. "The harps are pliable, so you can manipulate them a bit to ensure that the shades sit on the lamp properly," Ms. Contreras said. You should also orient the lampshade so that seams are hidden. "I can't begin to tell you how many seams I have seen on lampshades in movies, on television shows and even in magazines," she added. "You wouldn't put your dress on backward, would you?" "I'm all about the LEDs now," Ms. Contreras said. "Our home is illuminated by warm-colored LED bulbs, and they look like traditional incandescents. Plus, they're made for all fixtures, including recessed cans, table lamps and sconces." For a warm, inviting light, she said, go with 2,700 to 3,000 kelvin, often advertised as "warm white." As you go higher in the color-temperature range, she said, "more blue is introduced, and this ultimately gives that dreaded warehouse look." (Those bulbs — often advertised as "daylight" — do better in a garage or a more utilitarian space.) Like many other institutional structures assembled at the end of the twentieth century, the International Space Station (ISS) was designed to incorporate fluorescent light bulbs. At present, the spacecraft is more than halfway through a lighting overhaul, and its original bulbs are being replaced, piece by piece, with light-emitting diodes (LEDs). Compared with conventional incandescent or fluorescent bulbs, LEDs use less energy, last longer and contain no glass or mercury, negating the risk of glass shards or toxic metal floating through the space station should the bulbs break in zero gravity. But researchers also hope that the new lighting system will help astronauts to sleep better at night and to stay alert during the day. The problem that engineers are trying to address is that there's no 'day' or 'night' in space. The ISS circles Earth every 90 minutes or so, which provides astronauts with frequent opportunities to see the Sun rise and set, but also wreaks havoc on the body's roughly 24-hour, or circadian, clock. Among space flight's many deleterious effects on health, disturbance of the circadian rhythm and the sleep deprivation that accompanies it have emerged as considerable worries — particularly as people contemplate travelling to more distant locations in the Solar System, says George Brainard, director of the Light Research Program at Thomas Jefferson University in Philadelphia, Pennsylvania. The LED-based lighting system being introduced to the ISS is designed to target not just rods and cones — photoreceptor cells in the eye that enable vision in dim light and in colour, respectively — but also a third type of photoreceptor cell that was discovered almost 20 years ago. Known as intrinsically photosensitive retinal ganglion cells (ipRGCs), these photoreceptors contain a light-sensitive protein called melanopsin. They don't have much of a role in vision; instead, ipRGCs serve as the body's main entry point for light that regulates biological functions such as the sleep–wake cycle, alertness and mood. Researchers are beginning to understand the extent to which too much or too little light at the wrong time of day can throw important physiological processes out of sync, whether you're an astronaut on a spacecraft, a nurse on the night shift, or just playing computer games after bedtime. Artificial lighting has extended the length of time for which people are exposed to light each day, for better or for worse. LED-based dynamic lighting systems that are capable of adjusting the colour and intensity of the light that they deliver should make it possible to design lit environments that are less detrimental to health. "There's no limit to the technology in terms of what can be done with LED lights," says Robert Lucas, a neuroscientist at the University of Manchester, UK, who studies the visual system's response to light. "That puts the onus on us, as biologists, to tell the lighting engineers exactly what they should be doing."