Illuminance

Part of speech: noun

Definitions

1. The quantification of light intensity falling on a surface per unit area is referred to as a specific measurement in lux
2. A precise evaluation of brightness reaching a surface area can be expressed in terms of luminous flux density
3. The measure of the amount of light that strikes a particular surface area, expressed in units that quantify luminous flux per unit area

Etymology: Illuminance is a late coinage from the physics of light, and it was built from parts that already existed in English. It is formed from "illuminate," which goes back to the Latin "illuminare," meaning to light up or shed light on, with the suffix "-ance" added to turn the verb into a noun for a quantity. Its meaning is precise: it measures how much luminous flux falls on a given surface area, usually expressed in lux, where one lux is one lumen per square metre. The distinction it makes is what sets it apart from its near-relatives. A lamp emits light, measured as luminous flux in lumens, but the same lamp produces very different illuminance depending on how far away the surface is and how the light strikes it. The term lets photographers, architects and lighting engineers talk about the light arriving at a desk or a film sensor rather than the light leaving the bulb.

Synonyms: brightness, luminance, radiance, light, glow

Antonyms: darkness, dimness, dullness