Explanation

Lux is the unit of illuminance (illumination), which measures light falling on a surface. However, Luminous Flux is measured in lumens, and Lux is defined as lumens per square meter (lm/m²). Illumination is often used interchangeably with illuminance but technically refers to the concept, not the unit itself. Luminous Intensity is measured in candela (cd), which measures light emitted from a source in a specific direction. Focus is not a standard unit of light measurement.