VS - Lighting Systems - Lighting - 998542

5.3.4. The luminance

5.3.4.1. Daytime Running Light (DRL) luminance

L (cd/m 2 )

Daytime Running Lights belong to the signalling product family. DRLs are a perfect example of a high luminance application, they produce a huge intensity of light in a compact reflector. The ECE R87 regulation specifies an apparent surface between 25 cm² and 200 cm², and an intensity level between 400 and 1200 cd. The apparent surface and the intensity permit to calculate and see how huge can be the maximum luminance level on Daytime Running Lamps (480000 cd/m 2 ).

The luminance measures the reflected light from a surface to a given direction; the surface can itself be light-emitting, transmitting or reflecting light from another source.

The luminance is the perceived brightness, it is used to categorise:

ECE R87 Daytime Running Light luminance boundaries

ECE R87 Daytime Running Light luminance boundaries

l Light sources (eg. lamps). l Lighting systems (eg. headlights). l Any surface that is bright (eg. road signs). The luminance is related to a luminous intensity emitted per unit of area from a surface in a specific direction.

L (cd/m 2 )

400 to 1200 cd

I S

=L

Max. luminance: 480000 cd/m 2 Min. luminance: 20000 cd/m 2

25 to 200 cm 2

l Symbol: L l Unit: Candela per m 2

Where L is luminance, I is intensity of light and S is surface area of emitted light.

To summarise: - Illuminance (Lumen/m 2 ) is all the light that shines on a surface - Luminance (Candela/m 2 ) is the reflected light from a surface to one direction

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