Glossary

Directional lighting that is used to highlight a particular object or feature.

Provides an area with overall illumination. It emits a comfortable level of brightness without glare.

The beam angle of a light bulb is the angle at which light is emitted. Light bulbs with narrow beam angles are primarily designed to focus light onto an individual location whereas a lamp featuring a much larger beam angle will spread over a much large area.

The measure of luminous intensity of a light source in a given direction. When considering light bulbs which are to give light in a specific direction, the higher the candela the better the performance of the light bulb. A wide angle will generally reduce the candela as the light is being spread over a larger area.

The measure of luminous intensity of a light source in a given direction. When considering light bulbs which are to give light in a specific direction, the higher the candela the better the performance of the light bulb. A wide angle will generally reduce the candela as the light is being spread over a larger area.

A number indicating the degree of ‘yellowness’ or ‘blueness’ of a white light source. This is measured in Kelvin (K). Generally light sources are described as very warm white (2700K), warm white (3000K), cool white (4000K) and daylight (6500K).

Is a very accurate colour filter used to selectively pass light of a small range of colours while reflecting other colours. Dichroic reflectors commonly reflect visible light forward while allowing the invisible infrared light to pass out of the rear of the fixture, resulting in a beam of light that is literally cooler.

A device in an electrical circuit used for varying the brightness of a light source within a lighting installation.

A ceiling based light fitting either, recessed or surface mounted which concentrates the light in a downward direction.

Battery backed lighting used in the event of power failure for any particular reason. Luminaires types are usually either stand alone Non-maintained operation (emergency use only) or mains converted Maintained operation (mains + emergency use).

A recessed fitting that maintains the integrity of a fire rated ceiling in compliance of building regulations.

The standard unit for the measurement of colour temperature.

Measure of electrical power which equals 1000 watts.

A device that produces light or a container for such a device.

Light-emitting diode (LED) is a semi-conductor device that emits visible light when an electric current passes through it. Some advantages include – lower power requirement, high efficiency and longer lifetimes.

The ratio of light emitted by a luminaire to the total light output of the lamps it contains.

The measurement of the total amount of visible light from a light bulb or light source. The light may be emitted in a specific direction or in 360 degrees. The higher the lumen rating the brighter the light bulb will appear.

Lumen maintenance simply compares the amount of light produced from a light source or from a luminaire when it is brand new to the amount of light output at a specific time in the future.

The total light output emitted by a light source or received by a surface. Commonly known as lumens. Unit of measurement is lumens.

Is the ratio of the real power to apparent power and represents how much real power electrical equipment utilises.

Lighting that is designed into an application to illuminate an area for carrying out a specific task.

A device used for reducing or increasing the voltage of an alternating current.

This is the voltage at which the light bulb will operate normally. The standard for the UK is 240 volts.

A unit of electrical power. It defines the energy consumption by the light bulb when it is in operation.