Luminance vs. Illuminance: What is the Difference?

The display industry is incredibly complex. Most people don’t have a clue about all the terminology and concepts within the field. People think in terms of brightness and dullness. However, things are much more intense than that. This article will explain the difference between luminance and illuminance. Hopefully, people will get a better understanding of the components involved in the display industry.


Luminance is an incredibly vital component of the display industry. If you don’t understand luminance, you’ll never fully understand how to measure a display accurately. In laymen’s terms, luminance refers to the amount of light that passes through, emits from, or reflects off an object. One can measure luminance using a luminance meter. Luminance meters determine how much light is passing through an object, so professionals can determine how much the light is affecting it. You can display the measure of luminance using candela per square meter.


Illuminance is another key term within the display industry. It’s essential to understand the difference between the two terms so you can adequately measure a display. Whereas luminance refers to the amount of light passing through an object, illuminance refers to the amount of light falling onto a given surface area. The best way to explain the difference between the terms is through an example. Imagine a lit-up streetlight. The amount of light that passes through the lightbulb refers to the luminance. On the other hand, the amount of light that hits the street below is illuminance. We measure illuminance in lux using an illuminance meter.

You must understand the difference between luminance and illuminance if you want to gain a deeper understanding of the display industry. Most people that don’t know about these terms refer to displays in terms of brightness. Yet, it’s crucial to know that luminance and illuminance aren’t synonymous with brightness. You can’t measure brightness; it’s something perceived by the human eye. Since both luminance and illuminance are quantifiable terms measured using specific tools, you’d be incorrect to use them interchangeably with brightness.