The LED Glossary is also available as a download (in German)

Candela (cd): The unit that describes the luminous flux emitted by a light source in a particular direction, such as in spots. A weak lamp (with a low lumen number) can brightly illuminate a small section of a spot due to the small beam angle (high candela number). The decisive factor in buying a spotlight is therefore not so much the luminous flux in lumens as the luminous intensity achieved at the desired beam angle (unit candela, cd).

Energy efficiency class: The energy efficiency classes of the EU energy consumption label show the consumer whether a product consumes much or little energy compared with an average product of the same type and size. The current classification for household lamps is A++ (very efficient) to E (inefficient). Few LED light sources currently meet the requirements of class A++. In the following class A+, LEDs and very efficient energy-saving lamps are found, while average products of these technologies are represented in class A. Low-voltage halogen lamps reach class B at the most, high-voltage halogen lamps are in classes C and D. The last in Class E of the new energy label for lamps are the last remaining reflector incandescent lamps on the market.

Colour temperature or light colour: The colour temperature is given in Kelvin. The many colour tones or light colours are mainly divided into three levels: warm white, neutral white and daylight white light. You can recognise the light colour by the colour temperature in Kelvin indicated on the package. The light colour should be chosen differently depending on the room and area of use (see table “Colour temperatures and light colours for different rooms and areas of use”).

Colour rendering / colour rendering index: is given in “Ra” and stands for the quality of the light in relation to the authenticity of the illuminated colours. An Ra value of 80 is a prerequisite for good lighting and is already required by law. This is sufficient for living areas. Graphic designers and designers, on the other hand, like to use particularly high-quality lamps with Ra values of over 90. A Ra of 100 stands for 100 percent natural colour rendering. Today, almost all light sources achieve values of over 80.

Half-value angle: provides information on how evenly lamps distribute their light. This is the angle of the light cone at which the luminous intensity of the lamp is at least half its maximum – which a 400 lumen LED, for example, illuminates to at least 200 lumens. LED lamps with a half value angle of 35 degrees are used for spot lighting, e.g. to illuminate an object, an image or the like with an LED lamp. To illuminate a room – for example in a ceiling luminaire – LEDs with a half value angle of 120 degrees are used.

Lamp: technically speaking, this refers only to the light source. These include incandescent bulbs, halogen lamps, energy-saving lamps and LED lamps.

LED: stands for Light Emitting Diode or light emitting diode.

Luminaire: describes the entire object. This includes the luminaire shade (lamp shade) and the light emitting unit, the light source.

Luminous efficacy (= energy efficiency): the luminous flux in lumen from a light source or luminaire divided by the total power consumption in watts (lumen per watt; Lm/W). The higher the luminous efficacy, the more efficient the lamp: it produces more brightness for the same wattage.

Lumen (lm): the unit of measurement (SI unit) of the luminous flux, i.e. the amount of light emitted by a lamp. Colloquially, the term brightness is often used instead of luminous flux.

Life cycle assessment: presents the environmental impacts, such as greenhouse gas emissions, caused by products on their “life cycle” from production to disposal and analyses the associated effects.

Mercury: is the only metal that is liquid at room temperature and can evaporate easily in contact with air. Mercury vapours are extremely toxic – inhaling only 0.1 – 1 mg a day leads to chronic poisoning, as 80 percent of the mercury inhaled is absorbed by the body and only about 20 percent is exhaled again. Compact fluorescent lamps (“energy-saving lamps”) contain small amounts of mercury – around two to five milligrams. From a medical point of view, this small amount is completely harmless if it escapes if the lamp breaks. Especially if the broken lamp is removed immediately and the room is extensively ventilated, there is no danger to health.

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