11
The Lighting Handbook
Luminous flux
The luminous flux describes the quantity light emitted
by light source.
Abbreviation: Phi Unit: Lumen
Abbreviation: Unit: Candela
Abbreviation: Unit: Lux
Abbreviation: Unit: cd/m2
Illuminance
Illuminance describes the quantity luminous flux falling on
a surface. measure
of light source’s economic efficiency. 12464 “Lighting indoor workplaces”).
The luminous efficiency the ratio the luminous flux
to the electrical power consumed (lm/W).
. Relevant standards specify the required illuminance
(e.
Luminous intensity
The luminous intensity describes the quantity light that
is radiated parti
cular direction. is
represented the luminous inten
sity distribu
tion curve
(LDC). This useful measure-
ment for directive lighting elements such reflectors.g.
It describes the one hand light source’s impression of
brightness, and the other, surface and therefore depends to
a large extent the degree reflection (colour and surface).
Illuminance: E(lx) =
luminous flux (lm)
area (m2)
Luminance
Luminance the only basic lighting para
meter that is
perceived the eye
