An explanation on lighting technology terms and jargon used in the industry.
Ceramic lamps
Ceramic metal halide lamps combine high output with great colour rendering and good efficiency. They produce light by passing an electric arc through a mixture of gases. In a metal halide lamp, the compact arc tube contains a high-pressure mixture of argon, mercury and a variety of metal halides.
Colour temperature
One aspect of lamp colour is its colour appearance – whether the light from the lamps looks ‘warm’ or ‘cool’ – measured by the correlated colour temperature (CCT). Lamps with a warm appearance having a CCT of 2700-3000K are generally considered appropriate in a domestic setting. Lamps of 4000K and above are considered ‘cool’ and are more appropriate for of ce and some retail applications.
CRI (Colour rendering index)
This is the ability of a light source to show surface colours as they should be, usually in comparison with a tungsten or daylight source. Lamps with poor colour rendering will distort some colours.
Colour rendering is usually assessed by the CIE colour rendering index (CRI or Ra) – a number between 0 and 100, where lower values indicate poor colour rendering and higher ones good colour rendering. CRI only works for approximately white sources. Guidance in the Cibse Code recommends lamps with CRI between 90 and 100 for inspection and colour matching. Where accurate colour judgement is required, such as in offices and shops, lamps with CRI over 80 are recommended. Researchers at NIST in the US have suggested that the colour rendering index is less suitable for LED spectra, especially in the way saturated colours like red and yellow are dealt with. They have proposed can alternative colour quality scale (CQS).
Chromaticity
Chromaticity is an objective specification of the quality of a colour regardless of its luminance as determined by its hue and colourfulness. It is the quality of a colour or light with reference to its purity and its dominant wavelength.
Dali
Dali stands for Digital Addressable Lighting Interface and is a controls protocol agreed by all the major manufacturers in the lighting industry. It is set out in the technical standard IEC 62386. The AG-Dali is a working group set up by the manufacturers and institutions in the field of digital lamp and luminaire control to promote Dali technology and applications.
kWh
The kilowatt-hour is a unit of energy equal to 1,000 watt-hours or 3.6 megajoules. The kilowatt-hour is most commonly known as a billing unit for energy delivered to consumers by electric utilities.
Lux
Lux is a measure of the light arriving on a surface. Lux is the international unit of illuminance and luminous emittance, measuring luminous ‑ ux per unit area. Illuminance is a measure of how much luminous ‑ ux is spread over a given area. One can think of luminous ‑ ux (measured in lumens) as a measure of the total amount of visible light present, and the illuminance as a measure of the intensity of illumination on a surface. The symbol for lux is lx. Illuminance can also be measured in foot candles, or fc.
Zhaga
Zhaga (not an acnonym) is an industry-wide cooperation aimed at standardising specifications for the interfaces of LED light engines. An LED light engine is an LED module and associated gear with defined interfaces that do not depend on the type of LED technology used inside the light engine. The aim of Zhaga is to enable interchangeability between products made by diverse manufacturers. Interchangeability is achieved by defining interfaces for a variety of application-specific light engines. Zhaga standards will cover the physical dimensions, as well as the photometric, electrical and thermal behaviour of LED light engines. Currently, the membership of Zhaga comprises manufacturers only.
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