Objectives
By the end of this lesson.
- Distinguish luminous flux, illuminance, luminous intensity and luminance.
- Understand why the same luminous flux does not guarantee the same result in a space.
Luminous flux
Luminous flux, expressed in lumens, describes the total quantity of visible light emitted. On its own, it does not indicate how that light is distributed or what illuminance will be achieved on a work surface.
Illuminance
Illuminance, expressed in lux, is the luminous flux received by a surface. It depends on the luminaire, its distribution, distance, geometry and reflections within the space.
Luminous intensity
Luminous intensity, expressed in candela, describes the light emitted in a given direction. It helps explain why two luminaires with the same luminous flux can produce very different results.
Luminance
Luminance concerns the light perceived from a direction and is relevant to contrast and glare analysis. It is particularly important when studying visual comfort.
