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Characteristics of Light

Lumen Scale

In the past, consumers have used wattage to rate the brightness of a lamp. However, wattage is not an accurate indicator of lamp brightness. Energy efficient light sources such as Compact Fluorescent Lamps (CFL) have much lower wattages while still producing a great amount of light. Wattage is simply a measure of the amount of energy consumed. Light output, on the other hand, is a measure of luminous flux or simply put, the brightness of the lamp. It is measured in LUMENS. More lumens = more light.




Correlated Color Temperature (CCT):

Warm or Cool Color appearance, or CCT, is measured in degrees Kelvin. Most light range between 2700K to 6500K. As a point of reference, daylight at noon has a Kelvin temperature of 5000K. Incandescent light sources typically range from 2700-3500K. Compact Fluorescents and LEDs can range from 2700-6500K. The higher the Kelvin temperature, the cooler the light source appears. Likewise, the lower the Kelvin temperature, the warmer the light source appears.




Color Rendering Index:

CRI (Ra), measures how well a given light source will render color. Scientists evaluate this by comparing 8 reference colors under two light sources: incandescent light (for warm color lamps) and daylight (for cool color lamps). CRI is represented by a number on a scale from 0 to 100 with 0 being "poor" and 100 being "excellent". The lower the number, the more distorted a color will look under the light source.



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