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Basic parameters used in lighting
Basic parameters used in lighting

Luminous flux

Luminous flux

Abbreviation: φ phi
Unit: lm lumen

The luminous flux describes the quantity of light emitted by a light source. The luminous efficiency  is the ratio of the luminous  flux to the electrical power consumed (lm/W). It is a measure of a lamp’s  economic efficiency.

Luminous intensity

Luminous intensity

Abbreviation: I
Unit: cd candela

The luminous intensity describes the quantity of 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: E phi
Unit: lx lux

Illuminance describes the quantity of luminous flux falling on a surface. It decreases by the square of the distance (inverse square law). Relevant standards specify the required illuminance (e.g. EN 12464 “Lighting of indoor work-places”).

E(lx) = luminous flux (lm) / area (m2)



Abbreviation: L
Unit: cd/m2

The luminance is the only basic lighting parameter that  is perceived by the eye. It specifies the brightness of  a surface and is essentially dependent on its reflectance (finish and colour).

SOURCE: Zumtobel Staff – The Lighting Book

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Edvard Csanyi

Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry facilities. Professional in AutoCAD programming.


  1. Fahad
    Aug 28, 2017

    A really basic and helpful article. Thanks.

  2. Albert simiyu
    May 11, 2015

    explain the technology how the quantity of natural lights controls the quantity of illumination of the building?

  3. tabokhadra
    Sep 25, 2012

    you should add UGR AND GLARE

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