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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.