Exterior Lighting 2012/2013 - Fergin AB

Planning aids
366 Planning aids
The luminous flux is the total luminous power
of a light source measured in Lumen and specified
by the lamp manufacturers for each lamp. For example:
an incandescent lamp has a luminous flux of
approx. 1400 Lm (14 Lm/Watt). In comparison to
this: a metal halide lamp has 9000 Lm (90 Lm/Watt).
The luminous intensity (l) is that part of
luminous flux radiating in a specific direction. It is
measured in candela (cd). The spatial distribution
of luminous intensity is generally demonstrated by
a polar light distribution curve.
The beam angle ( ) (also known as half beam
angle) (γ) characterizes the light distribution of a
luminaire.
At the angle shown, the luminous intensity is half of
maximum. In the case of rotationally symmetrical
reflectors, the beam angle can be described with
one value. In all other cases, the values of the two
main beam planes at half of max. luminous intensity.
The main beam angle shows the area in
which the largest proportion of light leaves the
asymmetrical) reflector.
The light density (L) is the measurement of the
brightness impression for the human eye, created
by a luminous or illuminated area. This is the only
"visible" photometric parameter. It is measured in
candela per square metre (cd/m 2). The luminous
intensity related to a visible surface is the light
density.
visible area (A · cos )
light intensity (l)
illuminated area(A)
l
L=
A·cos
The illuminace (E) is the unit of measurement for
the intensity of the light falling onto an illuminated
surface. It is calculated from the luminous flux ( )
and the size of the illuminated area A:
E =
A
luminous flux
surface
(with vertical light incidence to plane [A]).
The luminous flux is reduced by the factor cos
( = angle of inclination to surface A).
Since the light distribution and consequently the
illuminance vary from point to point, the average
illuminance value "E m", is taken as basis for planning
(unit of measurement: Lux (Lx).