The Society of Light and Lighting
is part of the Chartered Institution
of Building Services Engineers
The Society of
Light and Lighting
The SLL
Lighting
Handbook
The Society of
Light and Lighting
The SLL Lighting Handbook
The Society of
Light and Lighting
The SLL Lighting Handbook
222 Balham High Road, London SW12 9BS
+44 (0)20 8675 5211
www.cibse.org
Final Lighting book artwork 08 25/3/09 10:04 Page 1
This document is based on the best knowledge available at the time of publication. However,
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The rights of publication or translation are reserved.
No part of this publication may be reproduced, stored in a retrieval system or transmitted in

complementary to the SLL Code for lighting but to go beyond it in terms of applications and
background information without getting into the fine detail of the Lighting Guides.
The SLL Lighting Handbook is intended to be the first-stop for anyone seeking information on
lighting. It is aimed not just at lighting practitioners but also at lighting specifiers and students of
lighting. For all three groups, we have tried to make it comprehensive, up-to-date and easily
understandable. The contents summarise the fundamentals of light and vision, the technology of
lighting and guidance on a wide range of applications, both interior and exterior.
Authors
Peter Boyce PhD, FSLL, FIESNA
Peter Raynham BSc MSc CEng FSLL MCIBSE MILE
Acknowledgements
John Fitzpatrick
Lou Bedocs (Thorn Lighting)
Ted Glenny (Philips Lighting)
Jennifer Brons for Figure 20.2
Kit Cuttle for Figures 13.1 and 13.2
Lighting Research Center for Figures 9.1, 10.3, 18.8, 18.9 and 20.3
McGraw Hill Inc, for Figures 2.4 and 2.9
Mick Stevens for Figures 20.3 and 22.1
The Illuminating Engineering Society of North America for Figures 1.5, 1.6, 1.7, 1.8, 2.8 and 2.13
Philips Lighting, iGuzzini Illuminazione, Havells Sylvania & Luxo
Charlotte Wood Photography for Figures 14.1, 14.2 and 14.3
Editors
Stuart Boreham (entiveon Ltd.)
Peter Hadley (Squarefox Design Ltd.)
SLL Secretary
Liz Peck
CIBSE Editorial Manager
Ken Butcher
CIBSE Director of Information

2.1.2 Eye movements
2.1.3 Optics of the eye
2.1.4 The structure of the retina
2.1.5 The functioning of the retina
2.1.6 The central visual pathways
2.1.7 Colour vision
2.2 Continuous adjustments of the visual system
2.2.1 Adaptation
2.2.2 Photopic, scotopic and mesopic vision
2.2.3 Accommodation
2.3 Capabilities of the visual system
2.3.1 Threshold measures
2.3.2 Factors determining visual threshold
2.3.3 Spatial thresholds
2.3.4 Temporal thresholds
2.3.5 Colour thresholds
2.3.6 Light spectrum and movement
2.4 Suprathreshold performance
2.5 Visual search
2.6 Visual discomfort
2.6.1 Insufficient light
2.6.2 Illuminance uniformity
2.6.3 Glare
2.6.4 Veiling reflections
2.6.5 Shadows
2.6.6 Flicker
1
1
3
3

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2.7 Perception through the visual system
2.7.1 The constancies
2.7.2 Attributes and modes of appearance
2.8 Anomolies of vision
2.8.1 Defective colour vision
2.8.2 Low vision
PART 2: TECHNOLOGY
Chapter 3: Light sources
3.1 Production of radiation
3.1.1 Incandescence
3.1.2 Electric discharges
3.1.3 Electroluminescence
3.1.4 Luminescence
3.1.5 Radioluminescence
3.1.6 Cathodoluminescence
3.1.7 Chemiluminescence

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4.3.2 Classification
Chapter 5: Electrics
5.1 Control gear
5.1.1 Ballasts for discharge light sources
5.1.2 Transformers for low voltage light sources
5.1.3 Drivers for LEDs
5.2 Lighting controls
5.2.1 Options for control
5.2.2 Input devices
5.2.3 Control processes and systems
PART 3: APPLICATIONS
Chapter 6: Lighting design
6.1 Objectives and constraints
6.2 A holistic strategy for lighting
6.2.1 Legal requirements
6.2.2 Visual function
6.2.3 Visual amenity
6.2.4 Lighting and architectural integration
6.2.5 Energy efficiency and sustainability
6.2.6 Maintenance
6.2.7 Lighting costs
6.2.8 Photopic or mesopic vision
6.2.9 Light trespass and skyglow
6.3 Basic design decisions
6.3.1 Use of daylight
6.3.2 Choice of electric lighting system
6.3.3 Integration
6.3.4 Equal and approved
Chapter 7: Daylighting
7.1 Benefits of daylight

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7.5 Types of daylighting
7.5.1 Windows
7.5.2 Clerestories
7.5.3 Rooflights
7.5.4 Atria
7.5.5 Remote distribution
7.5.6 Borrowed light
7.6 Problems of daylighting
7.6.1 Visual problems
7.6.2 Thermal problems
7.6.3 Privacy problems
7.7 Maintenance
Chapter 8: Emergency lighting

9.2.3 Screen type
9.2.4 Daylight availability
9.2.5 Ceiling height
9.2.6 Obstruction
9.2.7 Surface finishes
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9.4.1 Direct lighting
9.4.2 Indirect lighting
9.4.3 Direct/indirect lighting
9.4.4 Localised lighting
9.4.5 Supplementary task lighting
9.4.6 Cove lighting
9.4.7 Luminous ceilings
9.4.8 Daylight
Chapter 10: Industrial lighting
10.1 Functions of lighting in industrial premises
10.2 Factors to be considered
10.2.1 Legislation and guidance
10.2.2 The environment
10.2.3 Daylight availability
10.2.4 Need for good colour vision
10.2.5 Obstruction
10.2.6 Directions of view
10.2.7 Access
10.2.8 Rotating machinery
10.2.9 Safety and emergency egress
10.3 Lighting recommendations
10.3.1 Control rooms
10.3.2 Storage
10.3.3 Ancillary areas
10.3.4 Speculative factory units
10.4 Approaches to industrial lighting
10.4.1 General lighting
10.4.2 Localised lighting
10.4.3 Local lighting
10.4.4 Visual inspection

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x
11.3 Lighting recommendations
11.3.1 Illuminances
11.3.2 Illuminance uniformity

13.1 Functions of lighting in museums and art galleries
13.2 Factors to be considered
13.2.1 Daylight or electric light
13.2.2 Conservation of exhibits
13.2.3 Light source colour rendering properties
13.2.4 Adaptation
13.2.5 Balance
13.2.6 Shadows and modelling
13.2.7 Glare
13.2.8 Veiling reflections and highlights
13.2.9 Out-of-hours activities
13.2.10 Security and emergency
13.2.11 Maintenance
13.2.12 Flexibility
13.3 Lighting approaches for museums and art galleries
13.3.1 Wall mounted displays
13.3.2 Three-dimensional displays
13.3.3 Showcase lighting
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Chapter 14: Lighting for hospitals
14.1 Functions of lighting in hospitals
14.2 Factors to be considered
14.2.1 Daylight
14.2.2 Lines of sight
14.2.3 Colour rendering requirements
14.2.4 Observation without disturbance to sleep
14.2.5 Emergency lighting
14.2.6 Luminaire safety
14.2.7 Cleanliness
14.2.8 Electro-magnetic compatibility (EMC)
14.3 Approaches for the lighting of different areas in hospitals
14.3.1 Entrance halls, waiting areas and lift halls
14.3.2 Reception and enquiry desks
14.3.3 Hospital streets and general corridors
14.3.4 Changing rooms, cubicles, toilets, bath,
wash and shower rooms
14.3.5 Wards
14.3.6 Reading lighting
14.3.7 Night lighting
14.3.8 Night observation lighting (watch lighting)

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17.2.7 Impact on the surrounding area
17.2.8 Atmospheric conditions
17.3 Lighting recommendations
17.3.1 Illuminance and illuminance uniformity
17.3.2 Glare control
17.3.3 Light source colour properties
17.3.4 Loading areas
17.3.5 Chemical and fuel industries
17.3.6 Sidings, marshalling yards and goods yards
17.4 Approaches to exterior workplace lighting
17.4.1 High mast floodlighting
17.4.2 Integrated lighting
17.4.3 Localised lighting
Chapter 18: Security lighting
18.1 Functions of security lighting
18.2 Factors to be considered
18.2.1 Type of site
18.2.2 Site features
18.2.3 Ambient light levels
18.2.4 Crime risk
18.2.5 CCTV surveillance
18.2.6 Impact on the surrounding area
18.3 Lighting recommendations
18.3.1 Illuminance and illuminance uniformity
18.3.2 Glare control
18.3.3 Light source colour properties
18.4 Approaches to security lighting
18.4.1 Secure areas
18.4.2 Public spaces
18.4.3 Private areas

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Chapter 19: Sports lighting
19.1 Functions of lighting for sports

20.4.2 Interior lighting
20.4.3 Exterior lighting
20.5 Measurement of illuminance variation
20.5.1 Illuminance diversity
20.5.2 Illuminance uniformity
20.6 Luminance measurements
20.7 Measurement of reflectance
Chapter 21: Lighting maintenance
21.1 The need for lighting maintenance
21.2 Lamp replacement
21.3 Cleaning luminaires
21.4 Room surface cleaning
21.5 Maintained illuminance
21.6 Designing for lighting maintenance
21.7 Determination of maintenance factor for interior lighting
21.7.1 Lamp lumen maintenance factor (LLMF)
21.7.2 Lamp survival factor (LSF)
21.7.3 Luminaire maintenance factor (LMF)
21.7.4 Room surface maintenance factor (RSMF)
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21.8 Determination of maintenance factor for exterior lighting
21.9 Disposal of lighting equipment
Chapter 22: On the horizon
22.1. Changes and challenges
22.2. The changes and challenges facing lighting practice
22.2.1 Costs
22.2.2 Technologies
22.2.3 New knowledge
22.2.4 External influences
22.3 The evolution of lighting practice
Chapter 23: Bibliography
23.1 Standards
23.2 Guidance
23.3 References
Index
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287
287
287
287

Observer to characterise the spectral sensitivity of the human visual system by day.
Wavelength (m)
RADIO
WAVES
MICRO
WAVES
INFRA
RED
ULTRA
VIOLET
X RAYS
GAMMA
RAYS
COSMIC
RAYS
780 nm
380 nm
VISIBLE
10
4
10
2
10
0
10
–2
10
–4
10
–6

the lighting industry to quantify the efficiency of a light source at stimulating the rod
photoreceptors of the eye (see Section 2.1.4).
The CIE Standard and Modified Photopic Observers and the CIE Standard Scotopic
Observer are shown in Figure 1.2, the Standard and Modified Photopic Observers having
maximum sensitivities at 555 nm and the Standard Scotopic Observer having a maximum
sensitivity at 507 nm. These relative spectral sensitivity curves are formally known as the
1924 CIE Spectral Luminous Efficiency Function for Photopic Vision, the CIE 1988 Modified
Two Degree Spectral Luminous Efficiency Function for Photopic Vision, and the 1951 CIE
Spectral Luminous Efficiency Function for Scotopic Vision, respectively. More commonly,
they are known as the CIE V (
λ
), CIE V
M
(
λ
), and the CIE V’ (
λ
) curves. These curves are
the basis of the conversion from radiometric quantities to the photometric quantities used to
characterise light.
Figure 1.2 The relative luminous efficiency functions for the CIE Standard Photopic Observer,
the CIE Modified Photopic Observer, the CIE Standard Scotopic Observer, and the relative
luminous efficiency function for a 10 degree field of view in photopic conditions
Relative luminous
efficiency
= Standard photopic observer
= Modified photopic observer
= Standard scotopic observer
= 10 degree field
Wavelength (nm)

flux in lumens (lm). The values of K
m
are 683 lm/W for the CIE Standard and Modified
Photopic Observers and 1699 lm/W for the CIE Standard Scotopic Observer. It is always
important to identify which of the CIE Standard Observers is being used in any particular
measurement or calculation. The CIE recommends that whenever the Standard Scotopic
Observer is being used, the word scotopic should precede the measured quantity, i.e. scotopic
luminous flux. Luminous flux is used to quantify the total light output of a light source in
all directions.
Figure 1.3 The process for converting from radiometric to photometric quantities. The
lefthand figure shows the spectral power distribution of a light source in radiometric quantities
(watts/wavelength interval). The centre figure shows the CIE Standard Photopic Observer.
Multiplying the spectral power at each wavelength by the luminous efficiency at the same
wavelength given by the CIE Standard Photopic Observer, the right hand figure is produced.
The right hand figure is the spectral luminous flux distribution in photometric quantities
(lumens/wavelength interval).
1.3.2 Luminous intensity
Luminous intensity is the luminous flux emitted/unit solid angle, in a specified direction. Solid
angle is given by area divided by the square of the distance and is measured in steradians. An area
of 1 square metre at a distance of 1 metre from the origin subtends one steradian. The unit of
measurement of luminous intensity is the candela, which is equivalent to one lumen/steradian.
Luminous intensity is used to quantify the distribution of light from a luminaire.
Φ
= K
m
Σ
Ψ
λ
V
∆

the surface and the geometry between the lighting, surface and observer.
There are two other quantities commonly used to express the relationship between the
luminance of a surface and the illuminance incident on it. For a perfectly diffusely-reflecting
surface, the relationship is given by the equation:
luminance =
where luminance is expressed in candela/m
2
and illuminance is expressed in lumens/m
2
.
1.3.3 Illuminance
Illuminance is the luminous flux falling on unit area of a surface. The unit of measurement of
illuminance is the lumen/m
2
or lux. The illuminance incident on a surface is the most
widely used electric lighting design criterion. Figure 1.4 shows some typical illuminances on
different surfaces under the noonday sun in temperate climates.
100 lux 2500 lux 5000 lux 10,000 lux 100,000 lux
(illuminance × reflectance)
π
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5
Chapter One: Light
For a diffusely-reflecting surface, reflectance is defined as the ratio of reflected luminous
flux to incident luminous flux. For a non-diffusely-reflecting surface, i.e. a surface with some
specularity, the same equation between luminance and illuminance applies but reflectance
is replaced with luminance factor. Luminance factor is defined as the ratio of the luminance
of the surface viewed from a specific position and lit in a specified way to the luminance of a
diffusely-reflecting white surface viewed from the same direction and lit in the same way. It
should be clear from this definition, that a non-diffusely-reflecting surface can have many

the solid angle of the cone, i.e. luminous flux/unit
solid angle
The luminous flux/unit area at a point on
a surface
The luminous flux emitted in a given
direction divided by the product of the projected
area of the source element perpendicular to the
direction and the solid angle containing that
direction, i.e. luminous intensity/unit area
The ratio of the luminance of a surface to the
illuminance incident on it
The ratio of the luminous flux reflected from a
surface to the luminous flux incident on it
The ratio of the luminance of a reflecting surface
viewed from a given direction to that of a perfect
white uniform diffusing surface identically illuminated
luminance = (illuminance
× luminance factor) / π
luminance = (illuminance × reflectance ) / π
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6
Chapter One: Light
1.3.6 Obsolete units
Photometry has a long history that has generated a number of different units of
measurement for illuminance and luminance. Table 1.2 lists some of these obsolete units,
together with the multiplying factors necessary to convert from the alternative unit to the SI
units of lumens/m
2
for illuminance and candela/m
2

lumen/cm
2
lumen/ft
2
candela/m
2
candela/cm
2
candela/in
2
candela/ft
2
lumen/m
2
lumen/m
2
lumen/cm
2
lumen/ft
2
Multiplying factor
1.00
1.00
10,000
10.76
1.00
10,000
1,550
10.76
0.32

Asphalt road surface
Luminance (cd/m
2
)
1,910
300
140
120
20
2.0
0.01
Table 1.3 Typical illuminance and luminance values.
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7
Chapter One: Light
1.4 The measurement of light — colourimetry
Photometry does not take into account the wavelength combination of the light. Thus it is
possible for two surfaces to have the same luminance but the reflected light to be made up
of totally different combinations of wavelengths. In this situation, and provided there is
enough light for colour vision to operate, the two surfaces will look different in colour. The
CIE colourimetry system provides a means to quantify colour.
1.4.1 The CIE chromaticity diagrams
The basis of the CIE colourimetry system is colour matching. The CIE Colour Matching
Functions are the relative spectral sensitivity curves of the human observer with normal
colour vision and can be considered as another form of standard observer. The CIE colour
matching functions are mathematical constructs that reflect the relative spectral sensitivities
required to ensure that all the wavelength combinations that are seen as the same colour
have the same position in the CIE colourimetry system and that all wavelength
combinations that are seen as different in colour occupy different positions. Figure 1.5 shows
two sets of colour matching functions. The CIE 1931 Standard Observer is used for colours

Chapter One: Light
X = h Σ S(
λ
) x(
λ
)
λ
Y = h Σ S(
λ
) y(
λ
)
λ
Z = h Σ S(
λ
) z(
λ
)
λ
where: S(
λ
) = spectral radiant flux of the light source (W/nm)
x(
λ
), y(
λ
), z(
λ
) = spectral tristimulus values from the appropriate
colour matching function

chromaticity diagram is useful for indicating approximately how a colour will appear, a value
recognised by the CIE in that it specifies chromaticity coordinate limits for signal lights and
surfaces so that they will be recognised as red, green, yellow, and blue (CIE Publication
107:1994).
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Chapter One: Light
Figure 1.6 The CIE 1931 Chromaticity Diagram showing the spectrum locus, the Planckian
locus and the equal energy point)
The CIE 1931 chromaticity diagram is perceptually non-uniform. Green colours cover a
large area while red colours are compressed in the bottom right corner. This perceptual
non-uniformity makes any attempt to quantify large colour differences using the CIE 1931
chromaticity diagram futile. In an attempt to improve this situation, the CIE first introduced
the CIE 1960 Uniform Chromaticity Scale (UCS) diagram and then, in 1976, recommended
the use of the CIE 1976 UCS diagram. Both diagrams are simply linear transformations of the
CIE 1931 chromaticity diagram. The axes for the CIE 1976 UCS diagram are
u' = 4x / (–2x +12y +3) v' = 9y / (–2x + 12y + 3)
where x and y are the CIE 1931 chromaticity coordinates. Figure 1.7 shows the CIE
1976 UCS diagram.
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
520 nanometers
480 nanometers

780
2360
1900
1500
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Chapter One: Light
Figure 1.7 The CIE 1976 Uniform Chromaticity Scale diagram (from the IESNA
Lighting Handbook)
1.4.2 The CIE colour spaces
All chromaticity diagrams are of limited value for quantifying colour differences because
such diagrams are two-dimensional, considering only the hue and saturation of the colour.
To completely describe a colour a third dimension is needed, that of brightness for a self-
luminous object and lightness for a reflecting object. In 1964, the CIE introduced the U*, V*,
W* colour space for use with surface colours, where
U* = 13 W* (u – u
n
)
V* = 13 W* (v – v
n
)
W* = 25 Y
0.33
– 17 (where Y has a range from 1 to 100)
W* is called a lightness index and approximates the Munsell value of a surface colour (see
Section 1.4.7). The coordinates u, v, refer to the chromaticity coordinates of the surface
colour in the CIE 1960 UCS diagram while the chromaticity coordinates u
n
, v
n

U'
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