It specifies the brightness of a surface and is essentially dependent on its
reflectance. (finish and colour). Abbreviation: L. Unit: cd/m2. The Lighting
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The Lighting Handbook
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1st edition, July 2004
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The Lighting Handbook
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Chapter 1
Lighting fundamentals Chapter 2
Recommended values for indoor and outdoor lighting NEW: Based on the new European standards Chapter 3
Luminaires Chapter 4
Lamps and ballasts Chapter 5
Lighting and room management, Emergency lighting Chapter 6
By day we see in colour, while at night we can only see in shades of grey.
Chapter 1 / 3
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Basic parameters used in lighting Luminous flux – Luminous intensity – Illuminance – Luminance Luminous flux φ φ I= Ω
E=
φ A
Lumen [lm] Luminous intensity I
Illuminance E
Lux [lm/m2]=[lx]
Candela [lm/sr]=[cd] Luminance L L=
I A
L=
E Ω
[lm/(sr*m2 )]=[cd/m2 ]
Luminous flux
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Abbreviation: Unit:
φ lm
phi lumen
The Lighting Handbook
The luminous flux describes the quantity of light emitted by a light source. The luminous efficiency is the ratio of the luminous flux to the electrical power consumed (lm/W). It is a measure of a lamp’s economic efficiency.
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Luminous intensity The luminous intensity describes the quantity of light that is radiated in a particular direction. This is a useful measurement for directive lighting elements such as reflectors. It is represented by the luminous intensity distribution curve (LDC).
Abbreviation: Unit:
Ι cd
candela
Abbreviation: Unit:
E lx
lux
Abbreviation: Unit:
L cd/m2
Illuminance Illuminance describes the quantity of luminous flux falling on a surface. It decreases by the square of the distance (inverse square law). Relevant standards specify the required illuminance (e.g. EN 12464 “Lighting of indoor workplaces”). Illuminance: (lm) E(lx) = luminous flux area (m2)
Luminance
The Lighting Handbook
The luminance is the only basic lighting parameter that is perceived by the eye. It specifies the brightness of a surface and is essentially dependent on its reflectance (finish and colour).
Chapter 1 / 5
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General quality criteria for lighting The right light – traditional and new quality criteria T R A D I T I O N A L
N E W
Harmonious brightness distribution Sufficient illumination level
Glare limitation Avoidance of reflections
Good modelling Correct light colour Appropriate colour rendition
Quality criteria Changing lighting situations
Energy efficiency Daylight integration
Personal control
Light as an interior design element
Illuminance – definition of terminology Each term corresponds to the new European standards (see Chapter 2 / 2). Illuminance maintenance value Em: Value that the illuminance level must not fall below in the visual task area. Visual task area: Illuminance levels are specified for specific visual tasks and are designed for the area in which these may take place. If the precise location is not known, then the whole room or a specific working area is used to define it. The visual task area may be a horizontal, vertical or inclined plane.
Maintenance factor: The initial value multiplied by the maintenance factor gives the illuminance maintenance value. The maintenance factor accounts for the reduction in luminous flux from lamps, luminaires and room surfaces in the installation, and can be determined on a case-by-case basis. The maintenance schedule (the cleaning and maintenance intervals for the lamps and installation) must be documented. See also the chapter on “Economic efficiency calculation”.
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The Lighting Handbook
Area immediately surrounding the visual task area: Here the illuminance may be one level lower than in the visual task area (e.g. 300 lx to 500 lx).
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relative illuminance (%) initial value
150 125 100
maintenance value
75 50 25
operating time Maintenance value = maintenance factor x initial value
Glare – glare limitation
• luminaires with limited luminance levels • blinds
cause
The Lighting Handbook
• loss of concentration • more frequent mistakes • fatigue
• luminaires without glare control • very bright surfaces
Reflected glare
• loss of concentration • more frequent mistakes • fatigue
remedy
Direct glare
• matching luminaire to workstation (layout) • indirect lighting • matt surfaces Chapter 1 / 7
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Lighting technology Under the new European standard for interior workplace lighting EN 12464, (psychological) glare is assessed by the unified glare rating method (UGR), which is based on a formula for glare. It takes account of all the luminaires in a system contributing to the sensation of glare. UGR tables derived from this formula are provided by the manufacturers for glare rating. The Quickplan tables in Chapter 6 and the lighting catalogues contain reference values for specific room sizes.
(
UGR = 8 log 0,25 Lb (1)
L2 P2 (2)
)
The UGR method takes account of all the luminaires in the system that contribute to the glare sensation (2) as well as the brightness of walls and ceilings (1). It produces a UGR index. The two methods – the one set out in DIN 5035 and the one defined in EN 12464 – produce comparable results.
≤ 16 ≤ 19 ≤ 22 ≤ 25 ≤ 28
Technical drawing Reading, writing, training, meetings, computer-based work Craft and light industries Heavy industry Railway platforms, foyers
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The Lighting Handbook
UGR limits (UGRL), that must not be exceeded:
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The Lighting Handbook
1 45°
55°
65°
= 85°
= 45°
75°
8 103
2
3 4 5 6 8 104 2 Luminance L in cd/m2
A
3 4
2
8 6 4 3
a hs
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85°
Quality class for nominal illuminance (lx) A 1000 750 500
