LED Fact Sheet #17

Lux, Lumens and IES files ExplainedLux and Lumens are often confused.

“Lumens” is the total amount of light produced by the lamp or light fitting, while we use “Lux” as a

measure to know how much of that light is arriving on to a particular point of a surface.

Lux meters can be purchased cheaply to allow measurement of light on your working surfaces, but

the cost and complexity of accurately measuring Lumens is far greater.

The “efficacy” of an LED system is a calculation of how many Lumens are produced by a single Watt of

energy input. (Lumens/Watt or lm/W)

It is no longer relevant to talk about the “wattage” of LEDs in context of the brightness of the

luminaire. Don't be sold just on watts! High Lumens per Watt is the specification that will save you

energy.

The Illuminating Engineering Society (IES) created a system to provide lighting designers with a

method to create designs based upon the unique photometric signature of each light. IES files are

used daily to bring professional results to homes and business environments. Lighting designers

should be engaged for guidance whenever possible. All good LED lights should have an IES file

freely available.© Lumitex Ltd 2017