Glossary of Lighting Terms

Colour Rendering Index (CRI) - A quantitive measure of the ability of a light source to reproduce the colours of various objects faithfully in comparison with an ideal or natural light source. Values of 100-90 are very good, 90-80 good and LEDs with an Ra below 80 should not be used where people are working continuously.

Colour Temperature -  The colour temperature of a light source is the temperature of an ideal black body radiator that radiates light of comparable hue to that of the light source. Colour temperatures over 5,000K are called cool colours (bluish white), while lower colour temperatures (2,700–3,000 K) are called warm colours (yellowish white through red)

Light Level - The incidence of light flux on a surface per unit of area, measured in lux. There is a difference between the vertical and horizontal light levels.

Lumen (lm) - Unit of luminous flux used to describer a quantity of light emitted by a source or received by surface.

Luminaire Efficiency - How well a luminaire uses the luminous flux of the lamp used. The ratio is calculated by dividing the total luminaire lumens by the total circuit watts.

Lux (lux) - The unit of illuminance, equal to one lumen per square metre (lm/m²).

Halcyon - Halcyon is an intelligent, wireless, circadian lighting system for your home.

Halcyon+ - Halcyon+ is an intelligent, wireless, retrofit lighting system for professional environments, such as offices, schools and care homes.

ChromaWhite2 - ChromaWhite2 is the technology behind Halcyon. Designed and manufactured in the UK by PhotonStar LED. ChromaWhite2  is optimised for non-visual receptors that entrain circadian rhythm.


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