VS - Lighting Systems - Lighting - 998542

5.3.2. The luminous flux

F (lm)

The luminous flux is the complete light output radiated from a light source.

l Symbol: Ø l Unit: Lumen (lm)

The Lumen unit is defined based on the human eye sensitivity curve The following illustrations show how a human eye perceives a light source depending on its colour composition. The red curve illustrates the sensitivity of the human eye to colours stimulus. It can be seen that a lot of colour peaks on source N°2 are close to the red line; This means that the peaks in source N°2 will be perceived by the human

eye as a higher luminance source than in source N°1.

The theoretical and ideal light source for a human eye would have a spectral decomposition fitting perfectly to the red line.

Below shows types of automotive bulbs and their light output in Lumen.

100

100

Source Nr.1

Source Nr.2 D2S - 3200 lm

80

80

H7 - 1500 lm

60

60

40

40

P21W - 460 lm

Relative power

Relative power

Same package and same power but the orange colour reduces our eye perception

20

20

PY21W - 280 lm

0

0

400

500

600

700

800

400

500

600

700

800

450

550

650

750

450

550

650

750

Colour wavelength (nm)

Colour wavelength (nm)

R5W - 10 lm

100

.1

Source Nr.2

Considering the same electrical power, the source colour strongly affects the luminous flux level!

80

60

40

Relative power

20

0

700

800

400

500

600

700

800

750

450

550

650

750

)

Colour wavelength (nm)

13