What is indicated by the term ‘luminance’?

Luminance refers to the amount of light emitted or reflected from a surface in a specific direction and is measured in terms of luminous intensity per unit area. It quantifies how much light passes through or radiates from a particular area, providing a measure that links the concept of brightness to an objective physical quantity. Luminance is essential in visual perception as it helps in understanding how surfaces appear in terms of brightness when lit by a light source.

In contrast, other terms related to light measurement, such as light intensity measured in candelas, refer more to the total amount of visible light emitted from a source rather than its distribution across a surface. Brightness perceived by the human eye is a subjective experience and can be influenced by context and surroundings, while light energy received per unit area typically relates to illuminance, which concerns the amount of light incident on a surface rather than the light emitted from it. Thus, the definition of luminance as luminous intensity per unit area accurately reflects its role and significance in visual perception.