Illumination refers to:

Illumination refers to the amount of light falling on a surface. It is a measurable quantity that affects how we perceive objects, their colors, and their details. In various contexts, especially in photography, architecture, and vision science, illumination is crucial because it determines how well an object can be seen and how its features and colors are presented.

While the perception of light intensity and quality of light as perceived by the human eye are important concepts in understanding light, they relate to the subjective experience and interpretation of light rather than the physical amount of light present on a surface. Similarly, the effect of light on color perception is a consequence of illumination but does not define the term itself. Thus, the definition of illumination is best captured by the amount of light that reaches a surface, making it a key concept in the study of optics and visual perception.