The performance and features of a light source needs to be matched to the lighting task being performed. In order to select the right light source for the job, you should consider important performance variables such as light output (Lumens), efficiency (Lumens/Watt ?technically referred to as 揺fficacy?, lamp life, and color rendering properties measured in terms of the Color Rendering Index (CRI). The CRI is a measure of the degree to which a light source renders colors that are close to true color. For practical purposes it is a number from 0 to 100; the higher the number, the closer to true color. The efficiencies of each type of light source can vary dramatically, so the choice of light source can have a dramatic impact on lighting energy costs. The performance characteristics and efficiencies of common light sources are shown in the table and chart below.