Picture showing an enceclopedia explaining lumen and other electrical terms

Lighting terms

Our goal is to make sure that you have the best light and lighting solution for your application. We have briefly clarified some lighting technology terms to provide you with some support when selecting the right lighting product!


The colour temperature or light colour is specified in Kelvin (K). The light colour is important when planning lighting and should be tailored to suit the lighting area. The light colour can vary from warm white (rather orange/yellow) to cool white (blue light). ELEKTRA works with the three light colours, warm white (3,000K), cool white (4,000K) and daylight white (6,400K).


Lumen (lm) is the amount of luminous flux output by a lamp in all directions. When evaluating various different illuminants with different light outputs (lumens per Watt), it has become more important to know both values for classifying an illuminant. Lumens for the description of the brightness and Watts to define the amount of energy required to generate this brightness and thus for the evaluation of the energy efficiency.


The lighting intensity or illuminance is stipulated in lux (lx) and describes the amount of light striking a surface. The distance from the light source and the radiating angle are important factors.

Colour rendering index (CRI)

The colour rendering index (Ra) describes how the colours will be rendered in the light of a lamp. Here the highest value Ra 100 represents daylight for the colour rendering of the illuminated object. The colour rendering index is dependent on the spectral composition of the light and is therefore important when selecting LEDs.

Energy efficiency and operating modes with LEDs

In general it can be said that LEDs require less current than conventional lamps. Approx. 30 % of the energy is converted into light thus making LEDs a very efficient light source. However, the best lights lose a large part of their advantages when they are operated with poor or incompatible drivers or resistors. We therefore recommend constant current controllers to avoid efficiency losses with LEDs. Connecting a constant current source results in a lower efficiency loss in the driver. For comparison: With the connection of a 12V or 24V constant voltage source there is an additional efficiency loss due to the necessity of including a ballast resistor in each unit.

Service Information News Download