ABCs of LEDs: Lighting Metrics

By Kim Banks on October 21, 2011

Have you ever been confused by some of the terminology surrounding LEDs - words like "efficacy" or "correlated color temperature?" If so, you're not alone. We recently attended an educational webinar, ABCs of LEDs, presented by Residential Lighting magazine. The course offered a wealth of information on LED lighting technology - including lighting metrics. Here's a quick overview of the key terms and what they mean:
  • Lumen - the most common measure of light output.

  • Watt - measure of electric power; the rate at which electric energy is transferred by an electric circuit.

  • Efficacy - the light output emitted by a light source, divided by the nominal light source wattage and expressed in lumens per watt (lm/W).

  • Correlated Color Temperature (CCT) - a measure of the color appearance of a white light source. CCT is measured on the Kelvin absolute temperature scale.

  • Color Rendering Index (CRI) - 0-100 scale used to compare the effect of a light source on the color appearance of its surroundings. A higher CRI means better color rendering, or less color shift. CRIs in the range of 75-100 are considered excellent.

Are there any other terms you have come across when considering LED lighting?