22 February 2023

Discover the definitions of key lighting terms to enhance your understanding of the art and science of lighting.


Absorption is the process of a material taking in light energy and converting it into another form of energy, such as heat. It is a key concept in lighting, as it is the process by which light is blocked or reduced. Absorption can be used to control the amount of light entering a space, as well as to reduce glare and improve the quality of light.


Backlighting is a lighting technique used to create a halo effect around a subject by placing a light source behind the subject. It is commonly used in photography and cinematography to create a dramatic effect and to separate the subject from the background. Backlighting can also be used to create a silhouette effect, where the subject is completely dark and only the outline is visible.

Beam Angle

The entire opening angle of the emitted light of a luminaire is called the beam angle. This in turn is determined by the design of the reflector. The narrower the beam angle of the reflector, the smaller and thus the brighter the illuminated surface becomes.


Binning is a method of grouping light-emitting diodes (LEDs) into sets of similar brightness. This is done by measuring the current and voltage of each LED and then sorting them into groups based on their output. Binning is used to ensure that LEDs of the same brightness are used in a lighting system, allowing for a more consistent and uniform light output.


Brilliance is the measure of the amount of light emitted from a source, usually expressed in lumens or candelas. It is the intensity of the light and is often used to describe the brightness of a light source. Brilliance is also used to describe the quality of the light, such as its clarity and sharpness.


Candela [ cd ] stands for the unit of luminous intensity, that is, the luminous flux per solid angle unit. It is usually given for directed light, for example with downlights, and serves to calculate the degree of the illuminance of a surface in relation to angle and distance.

CE Mark

CE Mark is a certification mark that indicates conformity with health, safety, and environmental protection standards for products sold within the European Economic Area (EEA). It is a mandatory conformity mark for products manufactured within the EEA, and demonstrates that the product has met the requirements of the applicable European legislation. The CE Mark is also accepted in other countries outside of the EEA, including Australia, as a sign of quality and safety.

Circadian Rhythm

Circadian Rhythm is an internal biological process that regulates the sleep-wake cycle and repeats roughly every 24 hours. It is driven by the body’s natural circadian clock, which is influenced by environmental cues such as light and temperature. Circadian Rhythm is important for maintaining optimal health and well-being, as it helps to regulate hormones, metabolism, and other bodily functions.

Learn more about the Importance of Blue Light

Colour Temperature

Colour Temperature is a measurement of the colour of light, expressed in degrees Kelvin (K). It is a measure of the hue of a light source and is determined by the temperature of the light source. Colour Temperature is used to describe the colour of light emitted from a light source and is typically used to describe the colour of natural light sources such as the sun, or artificial light sources such as LED or fluorescent lighting. Colour Temperature is typically measured in a range from 1000K (warm) to 10,000K (cool). Warm light sources have a yellowish hue, while cool light sources have a bluish hue.
Learn more about Colour Temperature


Contrast is the difference in luminance or colour that makes an object (or its representation in an image) distinguishable. It is the range of luminance or colour values between the lightest and darkest areas of a space. High-contrast spaces or images have a greater range of luminance or colour values, while low contrast means there is a have a smaller range.

Cylindrical Illuminance

Cylindrical Illuminance is a measure of the amount of light that is emitted from a light source in a cylindrical shape. It is expressed in lux (lx) and is calculated by taking the total luminous flux emitted from the light source and dividing it by the area of the cylinder. Cylindrical Illuminance is used to measure the amount of light that is emitted from a light source in a specific direction, such as a spotlight or a floodlight. It is also used to measure the amount of light that is emitted from a light source in a specific area, such as a room or a hallway.


DALI stands for ‘Digital Addressable Lighting Interface’. A two-way communication protocol is used to control lighting systems, such as LED lighting, from a central control system. It is based on a digital bus system, allowing for the control of multiple lighting fixtures from a single controller. DALI is a popular choice for commercial and industrial lighting applications, as it allows for the control of multiple lighting fixtures from a single controller. It is also used in residential applications, such as dimming and colour changing.

Daylight Factor

Daylight factor is a measure of the amount of natural light that enters a space through windows, skylights, and other openings. It is expressed as a ratio of the total amount of natural light entering the space to the total amount of artificial light that would be required to achieve the same level of illumination. The higher the daylight factor, the more natural light is available in the space.


Degradation is the process of reducing the quality of a light source over time due to wear and tear, or the gradual decrease in the intensity of a light source due to age. It is a common issue in lighting systems, and can be caused by a variety of factors, including the use of inferior components, poor maintenance, or exposure to extreme temperatures. Degradation can lead to a decrease in the efficiency of the lighting system, and can also cause a decrease in the lifespan of the light source.

Degree of Illuminance

Degree of Illuminance is a measure of the intensity of light falling on a surface, expressed in lux (lx) or foot-candles (fc). It is the amount of light energy per unit area, and is calculated by dividing the luminous flux by the area over which it is spread.

Degree of Reflection

Degree of Reflection is a term used to describe the amount of light that is reflected off a surface. It is measured in terms of the percentage of light that is reflected off the surface, with higher percentages indicating a higher degree of reflection. The degree of reflection is important in lighting design, as it affects the overall brightness and contrast of a space.


Dimming is the process of reducing the output of a lighting fixture, typically by adjusting the voltage or current supplied to the fixture. This is commonly achieved by using a dimmer switch, which is a device that controls the amount of power supplied to the fixture. Dimming is used to create different lighting effects and to conserve energy.

Efficiency (lm/W)

Efficiency (lm/W) is a measure of the amount of light produced by a light source, in relation to the amount of power consumed. It is expressed as lumens per watt (lm/W) and is a measure of how efficiently a light source converts electrical energy into visible light.


Flicker is a phenomenon in which the light output of a light source fluctuates rapidly, resulting in a visible change in brightness. It is caused by the rapid switching of the light source on and off, or by the variation of the voltage supplied to the light source. Flicker can be a problem in lighting systems, as it can cause discomfort and eye strain.


Glare is a type of lighting that is too bright and causes discomfort or disability to the viewer. It is caused by excessive brightness, contrast, or reflection of light directed at the eye, and can be caused by direct or indirect lighting sources. Glare can be reduced by using appropriate luminaires for the application and usage, shielding, and/or using light-diffusing materials.

Half Beam Angle

The half beam angle is also called beam angle, half-value angle or opening angle. It is the beam angle used most frequently in lighting technology and is therefore also frequently specified by the manufacturers. The half beam angle describes the meteorologically relevant range of radiation and thus defines an abstract limit that the human eye cannot perceive. It is the angle between two points at which the luminous intensity falls to 50% of the maximum value. The diameter of a light cone is also given with the help of the half beam angle.

Human Centric Lighting

A type of lighting system designed to improve the well-being of people by providing light that is tailored to the individual’s circadian rhythm. It uses light sources that mimic natural daylight and can be adjusted to provide the right amount of light at the right time of day. The system is designed to improve alertness, reduce fatigue, and improve overall well-being.

Learn more about our Beyond Vision Range

IES File

IES File: A file format developed by the Illuminating Engineering Society (IES) of North America, used to store photometric data for lighting fixtures. It contains information such as the light distribution pattern, intensity, and colour of a particular luminaire. The IES file is used to simulate the lighting performance of a luminaire in a virtual environment, allowing for accurate lighting design and analysis.

Illumination Classes

There are three types of illumination classes – pre-classification into M, P and C classes is based on the traffic situation and composition of traffic. Within these classes, further selection is based on additional parameters, such as the traffic volume, speed, the difficulty of the driving task, etc.

M classes: Mainly roads with motorised traffic, such as main roads and thoroughfares. Evaluation is based on the luminance method taking the road surface into consideration. In addition to the average illumination density, the overall and longitudinal uniformity are used as quality characteristics, as well as the environment illuminance ratio REI and the glare percentage value fTI .

P classes: Roads with a low volume of traffic and low speeds, as well as areas for pedestrians and/or cyclists. Evaluation is based on the average and minimum degree of illuminance.

C classes: Conflict zones, such as areas where the flow of traffic is split, intersections and junctions. These also include roundabouts and pedestrian crossings. Evaluation is based on the average degree of illuminance and uniformity.


LED (Light Emitting Diode): A semiconductor device that emits light when an electric current passes through it. LEDs are highly energy efficient, long-lasting, and have a wide range of applications in lighting, including general illumination, automotive lighting, and decorative lighting.

Light Control

Light control makes it possible to coordinate illumination to the requirements and applications in question. Various switching and dimming states can be saved as light scenarios in the appropriate control devices and used again as required.

Individual luminaires, a group of luminaires in a room, the entire lighting system in a building or the illumination of whole streets can be integrated into a light control system.

Light Distribution

Light Distribution is the manner in which light is spread across a given area. It is determined by the type of light source, its position, and the shape of the reflector or lens used. Light distribution can be either direct, where the light is focused in a single direction, or indirect, where the light is spread out in multiple directions. The type of light distribution used will depend on the application, with direct light being used for task lighting, and indirect light being used for ambient lighting.


Lumens (lm) are a unit of measurement of the total amount of visible light emitted by a source, equal to the amount of light emitted in a unit solid angle by a uniform point source of one candela.


Lux (lx) is a unit of illuminance, which is the amount of light that is incident on a surface. It is equal to one lumen per square metre and is used to measure the intensity of light in a given area. Lux is commonly used to measure the amount of light in a room or outdoor area, and is often used to compare the brightness of different light sources.

MacAdam Ellipse

MacAdam Ellipse is a method of quantifying the colour differences between two light sources. It is based on the work of British physicist and colour scientist, David MacAdam, who developed a series of ellipses to represent the colour differences between two light sources. The ellipses are based on the CIE 1931 colour space, and are used to measure the colour differences between two light sources. The MacAdam Ellipse is used to determine the colour rendering index (CRI) of a light source, which is a measure of how accurately a light source renders colours. The MacAdam Ellipse is also used to measure the colour temperature of a light source, which is a measure of the colour of the light emitted by the source.

Maintenance Factor (MF)

Maintenance Factor (MF) is a measure of the expected life of a luminaire, expressed as a ratio of the rated life of the luminaire to the rated life of the lamp. It is calculated by dividing the rated life of the luminaire by the rated life of the lamp, and is expressed as a percentage. The higher the MF, the longer the expected life of the luminaire.

Mounting Height

Mounting height is the vertical distance from the floor to the centre of the luminaire. It is typically measured in metres and is used to determine the appropriate light levels for a given space.

Protection Class

Protection Class is a rating system used to classify the degree of protection provided by an electrical enclosure against the ingress of solid foreign objects and water. It is based on the Ingress Protection (IP) Code, which is an international standard developed by the International Electrotechnical Commission (IEC). Protection Class ratings range from IP00 (no protection) to IP69K (highest level of protection). The higher the Protection Class rating, the greater the protection against dust, dirt, and water.

Learn More about IP & IK Ratings


Reflection is the process of light bouncing off a surface, such as a wall or other object, and returning to the source. Reflection is an important part of lighting design, as it can be used to create interesting shadows and highlights, as well as to create a sense of depth and atmosphere.


Refraction is the bending of light as it passes through a medium, such as air, water, glass, or other transparent material, due to the change in speed of the light as it passes through the medium. This change in speed causes the light to be bent, or refracted, at an angle. Refraction is an important part of the way light behaves and is used in many optical devices, such as lenses and prisms.

Safety Class

Safety Class is a classification system used to identify the degree of protection provided by an electrical device. It is based on the International Electrotechnical Commission (IEC) standard 60598 and is used to indicate the level of protection against electric shock, fire, and other hazards. Safety Class is divided into four categories: Class I, Class II, Class III, and Class IV. Class I devices are the most protected, providing the highest level of protection against electric shock, fire, and other hazards. Class II devices provide a lower level of protection, while Class III and Class IV devices provide the least protection.


UGR (Unified Glare Rating): A metric used to measure the amount of discomfort glare in a lighting system. It is calculated by taking into account the luminance of the luminaire, the size of the luminaire, the distance of the luminaire from the observer, and the angle of the luminaire relative to the observer. UGR is used to ensure that lighting systems are designed to provide a comfortable and safe environment for occupants.


Uniformity is a measure of the evenness of light distribution across a given area. It is the ratio of the maximum to minimum illuminance levels across the area, and is expressed as a percentage. A higher uniformity percentage indicates a more even distribution of light, while a lower percentage indicates a more uneven distribution.

Visual Comfort

Visual comfort is the subjective perception of a person’s comfort in a given environment, with regards to the amount of light present. It is a combination of factors such as brightness, contrast, glare, colour temperature, and the distribution of light. Visual comfort is important for a variety of reasons, including safety, productivity, and well-being. It is also an important factor in the design of lighting systems, as it can affect the overall aesthetic of a space.

Visual Task Area

The area of a room or space that is illuminated by a light source to enable a person to perform a task or activity. It is typically defined by the distance from the light source and the amount of light required for the task.


Voltage is the electrical potential difference between two points in an electrical circuit, measured in volts (V). It is the amount of energy required to move a unit of electrical charge between two points in a circuit. Voltage is the driving force behind the flow of electrical current in a circuit.


Wattage is the measure of electrical power consumed by a lighting fixture, expressed in watts (W). It is a measure of the rate of energy consumption and is used to calculate the total energy consumed by a lighting system. Wattage is an important factor in determining the efficiency of a lighting system, as higher-wattage fixtures consume more energy and generate more heat.

Working Plane

The horizontal or vertical surface that is to be illuminated is called the working plane. Depending on the purpose of the illumination, the standards define a mathematical reference point at which the degree of illuminance is rated. 
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