Basic parameters used in lighting
Luminous flux - Luminous intensity - Illuminance - Luminance
â„¦ = solid angle into which luminous flux is emitted
A = area hit by luminous flux
ALÂŸcosâ‚¬ = visible areas of light source
p = reflectance of area
Ï€ = 3.14
* = for diffuse surface areas
The luminous flux describes the quantity of light emitted by the light sources.
The luminous efficiency is the ratio of luminous flux to the electrical power consumed (lm/W). It is a measure of the light source's economic efficiency.
Abbreviation: Î¦ Phi Unit: lm Lumen
The luminous intensity describes the quantity of the light that is radiated in a particular direction. This is a useful measurement for directive lighting elements such 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)
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 impression of brightness, and on the other, a surface and therefore depends to a large extent on the degree of reflection (color and surface).
Abbreviation: L Unit: cd/m2