BASIC PARAMETERS USED IN LIGHTING
THE LIGHTING HANDBOOK – CHAPTER 1
Luminious flux – Luminious intensity – Illuminance – Luminance
Ω = solid angle into which luminous flux is emitted
A = area hit by luminous flux
AL · cosϵ = visible areas of light source
p = reflectance of area
π = 3.14
* = for diffuse surface areas
The luminous flux describes the quantity of light emitted by a light source.
The luminous efficency is the ratio of the luminous flux to the electrical power consumed (lm/W). It is a measure of a light source’s economic efficency.
Abbreviation: Φ Phi Unit: lm Lumen
The luminous intensity describes the quantity of light that is radiated in a particular direction. This is a useful measurement for directive lighting elements sush as reflectors. It is represented by the luminous intensity distribution curve (LDC)
Abbreviation: I Unit: cd Candela
Illuminance describes the quantity of luminous flux falling on a surface. Relevant standards specify the required illuminance (e.g. EN 12464 “Lighting of indoor workplaces”)
Illuminance: E(lx) = [𝑙𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝑓𝑙𝑢𝑥 (𝑙𝑚)] / 𝑎𝑟𝑒𝑎 (𝑚2)
Abbreviation: E Unit: lx Lux
Luminance is the only basic lighting parameter that is perceived by the eye.
It describes on the one hand a light source’s inpression of brightness, and on the other, a surface and therefore depends to a large extent on the degree of reflection (colour and surface).
Abbreviation: L Unit: cd/m2