Learn About Lighting

By Craig DiLouie, LC

While light can be produced in specific colors for a special aesthetic effect, white light is the standard in home lighting. The choice doesn’t stop there, however, as more than one shade of white can be produced by light sources. This choice becomes particularly important when considering light sources such as compact fluorescent lamps, or CFLs.

First, a little background. Light is actually made of colors – that is, individual wavelengths of energy that the eye sees as color. This concept is beautifully revealed in rainbows, or when a beam of light is shined through a prism.

An object is seen as a certain color, in fact, because that color is present both in the object and the light falling on it. Light falls on the object. The object absorbs all colors except one, which it reflects to the eye. The eye sees the object as that color.

A warm-white light enriches the colors of the red and orange fruit while dulling blue (left), while a cool-white light makes the bottles appear a rich blue while dulling oranges and reds (right). Photo by Paul Kevin Picone/P.I. Corp

While white light is produced by all of the colors of the rainbow in nature, not all colors are necessary to make white. The most important are red, blue and green. Electric light sources produce colors in varying intensities of color wavelengths, resulting in lights that produce specific colors, and multiple shades of white. A light source saturated in blue wavelengths and deficient in red and orange would make blueberries appear a rich blue, while dulling the color of an apple, and so on. This gives us the opportunity to use lighting to control how colors in a space appear.

How do we choose?

The lighting industry has developed a metric to help us evaluate and predict the color tone of light sources: color temperature, expressed in kelvins (K). This metric indicates at a glance the color tone of a light source and the light it produces.

Light sources are generally classified as “cool” (>4000K), which appear bluish-white; “neutral” (3000K-4000K), which appear white; or “warm” (<3000K), which appear orangish-white. Warm light sources are rich in red and orange wavelengths, bringing out warmer colors, including flesh tones. The light of a candle, for example, is about 2000K. Cool light sources are rich in blue and green wavelengths, bringing out cooler colors. Noon daylight, for example, is about 5000K.

When buying a light source such as a CFL, note the color temperature on the Lighting Facts packaging. CFLs are available in warm-white, imitating incandescent, and cool-white, like standard fluorescent lighting one typically sees in an office.

The right choice for a given space depends on simple preference. Traditionally, in U.S. and Canadian homes, incandescent lamps (light bulbs) have been used, which are very warm (about 2800-3000K) in color tone. Many people simply associate warm-white with intimacy and relaxation, and are more accepting of lower light levels at this color tone. In the office, cool-white or neutral-white light sources such as fluorescent are preferred. Many people associate cool-white with work. It is not uncommon to mix color temperatures in a home, with warm-white preferred in living spaces, and cool-white in utility and workspaces. In other countries such as Japan and Mexico, meanwhile, cool-white sources are preferred throughout the home, resulting in a high degree of popularity of CFLs.

LED lighting technology offers exciting possibilities with color tone selection. While light sources are typically controlled with either a switch (ON/OFF) or a dimmer (raise/lower), some premium LED systems offer the possibility of a third dimension of control—color selection. The color temperature of an LED luminaire (light fixture) could be tuned to preference from warm to cool based on function, time of day or general preference.

Color is how you light it—and the color temperature metric puts you in control.

Color temperature scale with approximate examples:

What You Need To Know About Shades Of White:

• White light is the combination of individual color wavelengths
• Varying intensities of wavelengths can produce colors and multiple shades of white
• Designers can use this to control how colors appear in a space
• Color temperature is the metric used to achieve this control