Lighting Alfresco

Specialist garden and architectural lighting for private gardens and restaurants
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Glossary of lighting terms

Below are a list of terms commonly used by lighting manufacturers, landscape designers and lighting engineers.

Ambient light - the existing level of light before lamps are added  - in the case of garden lighting this might be street lamps, internal house or restaurant/hotel lighting. Ambient light must be taken into account when selecting the correct colour temperature and wattage/intensity at the design stage.

Average life - used to describe the number of lamp burn hours until 50% of a sample batch have failed.

Colour appearance - used to describe the "warmth" or "coolness" of the light given off by a particular source lamp (measured in degrees kelvin (k) - see colour temperature below).

Colour rendering - describes the general appearance of colours of surfaces illuminated by a given source (compared with their appearance when illuminated by light from a reference source).

Colour temperature - using a degrees kelvin (k) scale, each light source is assigned a colour temperature. The gives a relative indication of the warmth (or coolness) of the colour appearance of a particular light source - for example, 3000k would indicate a warm light, and 6500k would indicate a cold light.

Diffused lighting - used to describe lighting from many directions where no one direction dominates.

Directional lighting - describes a lighting situation where the light emanates predominantly from one direction.

Illuminance - a measure of the amount of light falling on a given area divided by that area (unit of measure is Lux).

Isolux diagram - a cross-sectional plot of the contours of equal luminance for a given source.

Lamp - the source of light (bulb, flame, etc.).

Lumen - the unit of flux of light (measuring the amount of light emitted from a given source).

Luminaire - the assembly that controls the distribution of light from a lamp, the connection and fixings of that lamp, and any protection of that lamp (used to be referred to as a "light fitting").

Luminary - a natural light giving body such as the sun or moon.

Luminescent - emitting light without being hot.

Luminous - emitting light, glowing in the dark.

Lux - unit of illumination (Lumen m^-2)

Wattage - the unit of measure of power consumed by a lamp (calculated by multiplying the working voltage by the current drawn in amps at the given working voltage).

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