752
Elements of lighting Design
TECHNICAL DATA
Luminous flux (Fig. 1)
300
125
24
36
2000
400
90
LUMINANCE (Fig. 4)
If the light source is greater than a point, its size becomes relevant and the above
definition of luminous intensity can no longer be applied. We must therefore introduce
a new concept which determines the amount of light energy that is emitted either by
light sources or by reflection surfaces.
This photometric quantity is the luminance (L), which is defined as the ratio of the
source luminous intensity in the direction of an observer to the emitting surface as
seen by the same observer (or apparent surface).The unit of measurement is cd/
sqm. The fundamental relation is given by:
L=dI α/dA x cos α
Where 1 is the candlepower at the angle α; is the source area, cos α is the cosine of
the angle formed by the observer’s eye and the normal to the source.
EFFICIENCY
lm/W
ALO MBF FL comp.
FL tubolare
JM SAP-T SBP FLUX
lm
POWER
W
LAMP
TYPE
LUMINOUS FLUX (Fig.1)
It is the amount of luminous energy emitted in the space by a source in a period of
time. The luminous flux is identified by the symbol Φ, and is measured in lumens (lm).
A lumen is equal to the luminous flux emitted within a unit solid angle from a spot
source subtended at the centre of a sphere having a luminous intensity of 1 candela
in all directions. In the International System, the measuring unit for solid angle is the
steradian (sr), which gives the following relation: 1 lm =1 cd x sr.
As the luminous flux is the time rate of light emitted by a source, it must be considered as power from the dimensional point of view as it is energy divided by the unit of
time. An interesting extension of the concept of luminous flux as power is the concept
of luminous efficiency.
Luminous efficiency is the ratio of the luminous flux emitted by a light source to the
power input of the source. Through this value it is possible to assess the energy
saving provided by one lamp compared to another.
5000 17
6300 50
1800 75
3350 93
180000 90
48000 120
13500 150
cos
E=
Luminous intensity (Fig. 2-2)
BZ CLASSIFICATION (Fig. 3)
The BZ method defines project parameters to obtain a greater precision in calculations as compared to the standard method. In particular, this method classifies fixtures according to 10 standard distributions of luminous intensity, i.e. 10 increasingly
wide polar curves that can be represented by a simple mathematical formula. At this
point, the fixture is given a BZ classification.The higher the BZ label, the wider the
light beam and the mounting spacing that would ensure correct uniformity
BZ2
2 x cos3 α
BZ3
3 x cos2 α
BZ1
1 x cos4 α
BZ5
5 x cos α
BZ6
6 x (1+2 cos
BZ4
4 x cos1.5 α
α)
BZ8
8
BZ9
9 x (1+sen α)
BZ7
7 x (2+cos α)
BZ10
10 x sen α
90ϒ
90ϒ
60ϒ
BZ5
100
300
200
BZ5
400 BZ4
45ϒ
BZ3
45ϒ
BZ1
30ϒ
15ϒ
300
400
BZ2
500
600
30ϒ
90ϒ
200
BZ3
500
700
600
800
700
BZ1
0ϒ
15ϒ
60ϒ
60ϒ
45ϒ
BZ4
75ϒ
BZ2
100
BZ10
75ϒ
BZ10
BZ8
60ϒ
BZ6
45ϒ
45ϒ
45ϒ
30ϒ
30ϒ
30ϒ
15ϒ
30ϒ
15ϒ
Classification diagram (Fig. 3-1)
90ϒ
50
150
200
50 BZ9
100
200
300
250
0ϒ
300
15ϒ
15ϒ
0ϒ
75ϒ
60ϒ
BZ8 BZ7 150
BZ6
250
40
80
120
75ϒ
BZ9
60ϒ
BZ7
h
200
45ϒ
30ϒ
COLOUR TEMPERATURE
Colour temperature is defined as a balanced mixture of various colours. By this definition, the colour temperature of a lamp, measured in Kelvin, is extremely important
for the installation of a luminaire. The temperature of a lamp can be regarded as a
quality criterion of choice, just as the flux is the quantity criterion. The table on the
right lists some examples of the luminous output of various sources:
- Stearic candle flame
1800 K
- Incandescent lamp
2700 K
- WHITE fluorescent lamp
3500 K
- Sun at sunset
3500 K - 4000 K
- COOLWHITE fluorescent lamp
3000 K
- Sun at noon in Summer
5500 K
- Clear sky
6500 K
- DAYLIGHT fluorescent lamp
6000 K - 6500 K
Illuminamento (Fig. 5)
115ϒ
115ϒ
105ϒ
95ϒ
105ϒ
95ϒ
85ϒ
75ϒ
70
85ϒ
75ϒ
65ϒ
140
65ϒ
55ϒ
210
55ϒ
45ϒ
280
45ϒ
350
30ϒ
Classification diagram (Fig. 3-2)
1 lumen
Ip
160
45ϒ
15ϒ
sqm
POINT-TO-POINT METHOD (Fig. 6)
The method used to determine the horizontal illuminance at a specific site is commonly called “point-to-point” method. Its formula is:
Ip x Klm x cos3 α
Ep = where:
h2
Ep
= illuminance at a site (in lux)
Ip = candlepower referred to 1000 lm, at the relevant site
Klm = the luminous flux of the lamp
3
cos α =cube of the cosine of the angle between normal to the fixture and relevant siteesame
h2 =the distance between the source and calculation plane
90ϒ
90ϒ
800
15ϒ
0ϒ
90ϒ
60ϒ
ILLUMINANCE VALUES
Sunshine, blue sky
100.000lx
Cloudy sky
10.000lx
Starry sky without moon
10-4lx
Average street lighting
5-30lx
Minimum light for pedestrians
to avoid obstacles
0.2-1lx
Well-lit house
100-200lx
Commercial conc.
200-3000lx
Offices and sc.
300-2000lx
a tot =2 rad
100
lux=
dA
where dΦ is the luminous flux incident on the surface, dA is the surface area struck
by the flux. The measuring unit of illuminance is lux (lx), which is dimensionally
expressed as cd/sqm
a =1 rad
90ϒ
ILLUMINANCE VALUES
Midday sun
16x109 cd/m2
Sunset
6x106 cd/m2
Blue sky
8000 cd/m2
Cloudy sky
2000 cd/m2 Lawn
800 cd/m2
Snowy plane
3,2x104 cd/m2
Tallow candle
5000 cd/m2 NC 60W clear bulb
5x106 cd/m2 FL 18W
4000 cd/m2
JM 70W
1,5x107 cd/m2
ILLUMINANCE (Fig. 5)
The concept of illuminance is critical in illumination design. This value is useful to
determine he amount of light that is emitted by a source and is present on a surface.
The illuminance (E) is the density of the luminous flux incident on a surface:
dΦ
Lm
a =1
60ϒ
1
Illuminance (Fig. 4)
LUMINOUS INTENSITY (Fig.2)
Luminous intensity is the amount of light (l) emitted by a spot source which propagates in a given direction. This intensity is defined as the flux ratio Φ emitted
in any specified direction in a unit solid angle cone ω, which gives l=dΦ/dω. It is
the fundamental physical quantity in the International System and is measured in
candelas (cd). The XVI General Conference for Weights and Measurements in 1979
established that the intensity of 1 cd is equal to the intensity of a source that emits - in
a solid angle of 1 sr - the frequency and power monochromatic radiation Φ=1/683 W.
A standard international eyesight, defined by ClE, is used to determine the maximum
relative visibility value for radiations at a 555 nm wavelength. This value corresponds
to that of the source under consideration, which therefore has 1 Im.
Luminous intensity (Fig. 2-1)
cos
=1
P
metodo punto-punto (Fig.6)
35ϒ
420
25ϒ 15ϒ 5ϒcd/km5ϒ
35ϒ
15ϒ 25ϒ
Rendimento (Fig. 7)
LUMINOUS EFFICIENCY (Fig. 7)
Luminous efficiency is the ratio of the total luminous flux emitted by the lamps to the
total flux used by the fixture
Φu
n=
Φ tot
Since luminous efficiency is a ratio between two homogeneous quantities, it is nondimensional and is generally expressed as a percentage value. For fixture classification, luminous efficiency is divided into lower (ni) and upper (ns).
Elements of lighting Design
Ceiling lamp “DISTRIBUTION CURVES” (Fig. 8)
All measurements of the luminous intensity emitted by a fixture in any direction produce the “photometric solid”. Normally, information on the photometric solid is only
given with reference to two vertical orthogonal planes crossing the optical centre of
the fixture. The values of the luminous intensity (referred to 1000 lm) that are plotted
on a plane are called “distribution curves”. For indoor and street lighting fixtures,
these distribution curves are represented with polar coordinates. Photometric data
for indoor fixtures according to the applicable UTE and DIN 5040 classification is
available on request.
ceiling lamp distr. curves (Fig. 8) installation
85ϒ
75ϒ
65ϒ
55ϒ
75ϒ
65ϒ 85ϒ
75ϒ
55ϒ
65ϒ
45ϒ 55ϒ
35ϒ 45ϒ
35ϒ
115ϒ
3
108
105ϒ
95ϒ
85ϒ
75ϒ
Ø 8.56
3.5
45ϒ
15ϒ
25ϒ
79
m
60
Ø 11.42
125ϒ
70
115ϒ
105ϒ
95ϒ
85ϒ
75ϒ
35
35
70
65ϒ
105
55ϒ
45ϒ
140
45ϒ
35ϒ
lux
105
55ϒ
65ϒ
Ø 9.99
4
5ϒ 5ϒ 15ϒ 25ϒ 35ϒ
output
angles
(degrees)
Indirect light
output
height in m
175
35ϒ
25ϒ 15ϒ 5ϒcd/Klm5ϒ 15ϒ 25ϒ
luminous
intensity cd/kIm
light diameter on the working
plane (expressed in m)
distribution
curve
(cd/klm)
lengthwise
plane
ISOLUX DIAGRAM (Fig. 9)
This is composed of a number of lines connecting all the points on a surface at which
illuminance is the same. The lighting fixture is assumed to be mounted at 1 m height
with a 1 klm reference lamp. The co-ordinates d/h and l/h express the relationship
between the road width (l), the distance between two poles (d) and the height of
the poles (h).
SOCANDELA DIAGRAM (Fig. 10)
Isocandela diagrams result from the projection on a plane of candlepowers of a
given photometric solid having the same value. They are therefore the connection
lines of all points on a plane having the same candlepower.
coefficiente utilizzatore
lato marciapiede
posizionamento
centro luminoso
rapporto larghezza strada-altezza
-1
lato strada
60%
0
1
I
1
0
3
d
2
1
3
illuminance chart (Fig. 11)
4
5
luminous int.
cd/kIm
axb
K=
hu x (a+b)
The number of fixtures required for a specific lighting installation is calculated with
the following formula:
Em x (axb)
napp =
Cu x Cm x Φ
Where Em isthe required average illuminance in Iux, Cm is the maintenance factor
(new installation = 1), Φ is the flux emitted by the lamp(s) in lumen. The utilisation
coefficient Cu is found on the table in Fig. 6-2. Locate the row corresponding to the
K room index, and the column of the total reflection factors of the room walls.
Example: To illuminate the following room:
a = 7m, b = 5m,
h = 3m, hp.l. = 0.80m, with 350 lux on a new installation; the fixture used is: art601
Disanlens 2x36W.
The reflection factors are: ceiling = 0.7; frieze = 0.7; walls = 0.3; working plane =
0.1 so the column (as shown in Fig. 13-2) is the blue column 7731. The K room
coefficient is therefore:‑
hu = h - hp.l. = 3 - 0.8 = 2.20m
K = (7 x 5) / (2.20 x (7 + 5)) = 1.3 (red row)
then Cu = 0.45 (yellow rectangle).
The number of the fixtures is found to be:
napp = 350 x (7 x 5) / (0.45 x 1 x 6900) = 4
K 8873777377537731555155113311
0.6 0.45 0.42 0.34 0.28 0.31 0.24 0.23
0.8 0.53 0.49 0.41 0.34 0.37 0.29 0.28
1.0 0.59 0.55 0.47 0.40 0.41 0.34 0.33
1.3 0.65 0.61 0.53 0.45 0.46 0.39 0.38
1.5 0.69 0.65 0.58 0.49 0.50 0.43 0.41
2.0 0.76 0.71 0.65 0.55 0.55 0.49 0.47
2.5 0.80 0.75 0.69 0.59 0.58 0.53 0.51
3.0 0.83 0.78 0.73 0.62 0.61 0.56 0.53
4.0 0.85 0.80 0.76 0.65 0.63 0.59 0.55
5.0 0.88 0.83 0.79 0.67 0.65 0.61 0.58
Y
h
hu
hpl
a
150
X
60ϒ 40ϒ 20ϒ 0ϒ -20ϒ -40ϒ -60ϒ
isocandela curves (Fig. 10)
Room dim. (Fig.13-1)
135
120
105
90
75
60
45
30
15
lux
6
6
14
12
48
14
16
12
14
10
22
18
52
28
32
22
34
26
40
36
60
44
48
30
52
44
62
54
68
58
62
40
Example of a CIE table (Fig.13-2)
Classe
A (1.15)
B (1.5)
C (1.85)
D (2.2)
E (2.55)
Quality
Classification type of visual duty or activity
Illuminance
levels
quality
classes
2000
1000
2000
500
1000
2000
Illuminamento [lx]
<300
500
<300
1000
2000
500
1000
2000
<300
500
1000
<300
500
<300
85
8
6
4
3
65
2
55
66
60
72
72
80
72
74
48
Reflection values (as a percentage)
taken from the illuminance handbook
0000
0.21
0.26
0.30
0.35
0.38
0.43
0.46
0.49
0.50
0.52
LUMINANCE CHART (Fig. 14)
This chart is used to determine the direct glare produced by each fixture. Luminance
values for the two curves are plotted in relation to an observer looking to the fixture
from an angle of 45° to 85°. Values are represented on a logarithmic scale. Limit
curves border the area in which the luminance of the fixture cannot be considered as
glare. Each curve is referred to an average illuminance value on the working plane,
and is divided into five CIE quality classes: if the luminance curve son the left side of
the limit curves, glare is considered as acceptable. On table nr. 15 you will find the
prospectus concerning glare limitations, indicating when and where to use a fixture
with one, or another, quality classification (UNI 12464).
75
distance in m.
output angles
(degrees)
ILLUMINANCE CALCULATION USING THE CIE METHOD (Fig.13)
We will first calculate the K index of a room, where “a” and “b” are the sides and
hu is the height of the fixtures above the working plane
400
illuminance curve
2
80ϒ 60ϒ 40ϒ 20ϒ 0ϒ 20ϒ 40ϒ 60ϒ 80ϒ
b
ILLUMINANCE DIAGRAM (Fig. 11)
The illuminance diagram is used to facilitate the choice of the fixture for urban
decoration i.e. to illuminate underways, open areas: gardens and especially roads.
Illuminance values in lux are given on the Y axis, the distance from the light source is
given on the X axis. Unlike other charts, which are presented with relative reference
values (i.e. normalised installation height and luminous flux values), this chart shows
absolute values, the mounting height is real and the flux is the flux that is actually
emitted by the lamp. In this way, data shown are ready to be used.
m
cd/klm
Floodlight distr. curves (Fig. 12)
-40ϒ
Isolux diagram (Fig. 9)
h
100
Z
-60ϒ
distribution
curve (cd/klm)
lengthwise plane
200
-20ϒ
I/h
4 d/h
Illuminance space between spacing-to
one isolux and the next
height ratio
positioning h
fixture
300
0ϒ
20%
2
distribution
curve (cd/klm)
crosswide
plane
400
20ϒ
40%
h
“DISTRIBUTION CURVES” floodlight (Fig. 12)
As a floodlight beam is narrower than that of the above fixtures, polar coordinates
do not provide sufficiently detailed values. Therefore, the distribution curve is better
represented with Cartesian co-ordinates.
60ϒ
40ϒ
753
45
2
10
shielding
angle
2
3
4 5 6
3
8 10
2
3
longitudinal
curve
4
4 5 6 8 10
1
2
3
4
transversal
curve
A
B
C
D
E
very difficult visual duty
visual duty requiring high visual performances
visual duty requiring normal visual performance
visual duty requiring fair visual performances
for interiors where people are located in specific working positions but who also move from one area to another to carry out duties requiring fair visual performances.
INFORMATION
RECOMMENDED
Light emitted from a light fixture can be represented by a graphic system called
“distribution curves”. These are the union of points joining the various luminous
intensities emitted by a light source in every direction in space and making up the
“photometric solid”. By intersecting this solid with a number of planes, one can obtain
“distribution curves”. When these planes are described through polar coordinates
whose centres correspond to the center of the fixture, one obtains “polar distribution
curves”. These planes can also be made to rotate around an axis so as to explore
the photometric solid under every angle. According to the axis used for rotation, there
are different systems of planes determined by CIE standards. An alternative mode
of representing distribution curves would be substituting the polar description with a
description using the Cartesian coordinates. With this system, the narrow beam curves are more readable and this system is generally used in representing the luminous
intensity of floodlights. In this diagram, the values of the angles are positioned along
the x-coordinate, with zero in the middle of the graph, while the values of intensity are
positioned along the ordinate. The two planes normally represented are the transversal and the longitudinal ones, which in the CIE system correspond respectively to the
C0-C180 (continuous line) plane and the C90-C270 (broken line) plane.
TECHNICAL DATA