Choosing lighting wisely is crucial to interior design, because the lights used affect the way people see colors. Proper interior lighting lets you tell the difference between a navy blue and a black, and truly sets the tone of a room. Check out our quick guide to lighting design to let you optimize your illumination!

Warm Vs. Cool
The first thing to consider with interior design lighting is whether the colors in the room are warm or cool. Warm colors will look earthy or fiery and include red, yellow, orange or brown. Cool colors will remind people of water and include blues, greens, and purples. The various types of designer lights work best with certain colors and not so well with others. For example, incandescent light is usually an orange-yellow, so it enhances warm colors, but it dulls cool ones. Fluorescent lights are the opposite, saturating cool colors and diminishing warm shades. As a fine middle-ground, LED lights work with just about anything, enhancing the entire spectrum of colors depending on the type of diode used.

A color scale (courtesy of Wikipedia) with cool coloring on the left, and warm on the right

Color Rendering Index (CRI)

The Color Rendering Index indicates how “true” a light source is, mostly in comparison to natural sunlight. It’s essentially measure of how full the colors are under a given light source; the index ranges from 0 to 100, and the higher the number the better. Incandescent lights are so far the top of the heap in this department, as they have CRIs of 100. Fluorescent lights are generally weaker, usually holding around the range of 50, while LEDs usually work at a minimum of 80 with higher-end models coming in around 90+.

Lighting Location

Also important to a room’s light design is the actual placement of the light: overhead lighting tends to be the most natural of lighting, for it mimics the sun by acting from the top-down. Its effects on color will thus be similar to that of sunlight. Light from a floor or table lamp will be softer and more diffuse by comparison, as the light shines upwards and thus casts more shadows.

Room Lighting

The last warming rays of sunlight often dramatically affect the coloring of a room

The Impact of Sunlight

As the angle and amount of sunlight changes, so will the colors in a room. The direction in which a room faces (that is, the side with the windows) will affect its response to the sun's natural light. For example, light in a north-facing room will be bluish and cool. Bold, bright colors will show very well, while pale colors will seem more muted in comparison. In a south-facing room, sunlight will enhance both warm and cool colors.

East-facing rooms are great for warm colors—the sunlight will be warm and yellowy in the morning and then seem cooler later in the day. West-facing rooms get little light in the morning, which creates shadows and makes colors look dull. By contrast, evening sunlight in these rooms looks quite warm due to the effects of the setting sun.

The decorator, therefore, will have to know the way a given room is facing and the time of day in which it appears darkest and gloomiest in order to choose a light that will compensate for that deficit.

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