Room Lighting Basics Choosing the Proper Lamp for Your Needs

Room lighting basics—choosing the proper lamp for your needs.

Room lighting basics—choosing the proper lamp for your needs

The lumen scale: the real story behind brightness

For years, consumers have used wattage to rate the brightness of lamps. But wattage is not the most accurate indicator of brightness. Just take energy efficient light sources, such as LED’s. They have very low wattages yet still produce a great amount of light. Wattage is a measure of the amount of energy consumed by the lamp, not necessarily an indicator of how bright it will be. Luminous flux (light output), is a truer measure of the brightness of the lamp. This measurement is referred to as Lumens.

As energy efficient lamp technology advances, and electrical consumption (wattage) decreases, lumens will become one of the most important factors in lamp selection. A clear example is, again, the LED light sources which can use 80% less electricity, yet produce comparable light to their higher-wattage counterparts.

So as you consider the purchase of new energy efficient lamps, like compact fluorescent or LED, remember that more lumens mean more light.

Color Rendering Index

Color Rendering Index (Ra), measures how well a light source will render color. CRI is evaluated by using 8 reference colors, then comparing how they look under the light source being tested, to how those same colors appear under two reference sources: incandescent light (for “warm” color lamps) and daylight (for “cool” color lamps). CRI is represented on a scale from 0 to 100; 0 being "poor" and 100 being "excellent". The lower the number, the more distorted a color will look under the light source. The two pictures below illustrate how a light source can enhance or distort the colors of an object.

(add existing lighting color photos here)

Correlated Color Temperature: Warm or Cool

Color appearance, known as Correlated Color Temperature (CCT), is a measure of how “warm” or “cool” a light source appears to the human eye. The unit of measure is degrees Kelvin.

Most light sources have a Kelvin temperature in the range of 2700K to 6500K. As a point of reference, daylight (mid-day), has a Kelvin temperature of 5000K. Most incandescent light sources range from 2700-3500K. Compact fluorescent and LED lamps can range from 2700-6500K. The higher the Kelvin temperature, the cooler the light source appears. The lower the Kelvin temperature, the warmer the light source appears.