Understanding the difference between Luminance and Illuminance

June 17, 2017 8:41 am

With the numerous advances in lighting technology, it can sometimes be tough to determine the right light source unless the basics of light are understood.

The brightness of a lighting fixture is determined by the number of lumens produced. Technically, a lumen is a standard unit that measures the total amount of visible light emitted by a light source.  Many lighting manufacturers, purchasers, and users often evaluate fixtures brightness solely based on lumen output.  However, evaluating a LED lighting fixture on the basis of its lumen output can give users a distorted image of the fixture performance, as Lumen measures the light being emitted by the light source and not necessarily the amount of light perceived by a human eye for use in a particular application. Simply put, lumen output is an inappropriate means to measure the suitability of a lighting fixture for a given task.

Alternate to lumen output, measuring the amount of delivered light, formally termed as Illuminance is the best and most appropriate method for evaluating the LED lighting fixtures.  Illuminance is the intensity or degree of light falling on a surface area and is therefore not the amount of light produced by the light source. Illuminance is measured in term of footcandle or lux.  A footcandle equals one lumen incident per square feet whereas lux equals one lumen incident per square meter of the illuminated surface area. Footcandle in a way depicts how much useful light a fixture delivers at a task area. Useful light is, therefore, the portion of light output that is effectively directed to a task area, eliminating any wastage of light.

Knowing the difference makes all the difference. When it is about fixture performance, footcandles delivered are more important than lumens produced.  LED manufacturers should always prioritize the optimization of the light engine as a system to deliver maximum footcandles without compromising on fixtures performance or longevity.

At LEDPRO, we offer a wide range of LED LIGHTING products. To buy, please follow the link http://www.ledpro.com/.If you have any questions either about the product or our company please feel free to give a call toll-free! 1-877-595-4769

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