Lumen (lm)

What Does Lumen (lm) Mean?

A lumen (lm) is the International System of Units (SI) measurement for luminous flux (brightness). It is defined as: the amount of light emitted when considering a solid angle of one steradian (sr), from a source that discharges to an equal light in all directions, with the strength of one candela (cd). The unit is defined in terms of steradian because light spreads in all three dimensions, hence the angle must be observed.


Techopedia Explains Lumen (lm)

The lumen is often misinterpreted as the watt, which is inaccurate. The watt is the measure energy which, when supplied to a bulb, produces luminous light. The brightness of this light is measured in lumens. European Union legislation has set the criteria for light to be measured in lumens, supplied by a primary source. The amount of light emitted (lumens) depends on the type of source and spectrum of light.

In terms of technology, lumens are used to measure the brightness of devices such as monitors, televisions and projectors.


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Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…