Ambient temperature

The ambient temperature (TA) specifies the ambient temperature at which the luminaire may be operated. The more the ambient temperature deviates from the optimum value of 15 to 25 degrees Celsius, the greater the impact on the service life of the LED and the driver. For extreme applications from -60 to + 75 degrees Celsius, there are alternative products such as the Lucid nova eos.


Ampere (A) is the unit for current strength and indicates how much current flows through a line.

Beam angle

The beam angle indicates the angle at which the light is emitted. The larger the value, the wider the cone of light. With a narrower beam angle, more light is projected onto a desired area. With a wider beam angle, the light is distributed over a larger illuminated area. The position height of the luminaire also plays a decisive role in the beam angle. This can be simulated in our DIALUX planning software. Asymmetrical light emission occurs when the light is emitted through a lens at two different angles (figure 30 degrees/60 degrees).


The luminous intensity is measured in candela (cd). Luminous intensity can be understood in a similar way to illuminance, but here the luminous flux is measured per solid angle rather than per area. The luminous intensity therefore contains information about the concentration of the light source, i.e. how strongly the luminous flux is concentrated on a solid angle. A light source with a luminous flux of 1 lumen (which therefore emits light evenly in all directions) has a luminous intensity of 1 candela in all directions. If, for example, a reflector is used, the luminous intensity decreases in some directions and increases in others. However, the luminous flux of 1 lumen remains constant.

Color temperature/CCT (correlated color temperature)

The color temperature is derived from the radiation emitted by a so-called „black body“ (i.e. one that does not reflect light) when it is heated. The unit of color temperature is Kelvin (K). A lower color temperature (high red component) has a „warmer“ effect on the human eye, while a high color temperature (high blue component) has a „colder“ effect. This is referred to as warm white (3,000 K), neutral white (4,000 K), daylight white (5,000 K) and cool white (6,500 K). We therefore recommend a color temperature of 5,000 K which comes closest to a sunny day. This color tone can noticeably reduce fatigue and the error rate during work and increases efficiency.

Color rendering index (CRI, Ra)

The color rendering index (CRI) provides a measure of the naturalness of the color. The higher the color rendering index, which is referred to as the CRI or Ra value, the more natural the colors are rendered. The value can be between 0 and 100. Sunlight has a color rendering index of 100, which is particularly important in laboratories or production facilities that require high quality standards in terms of color recognition and color deviation.

Note: Whether a high color rendering index is required depends on the area of application of a luminaire. For example, a high Ra value is required in the printing industry, whereas this is not absolutely necessary in a warehouse. 

Constant Lumen Output (CLO)

The longer a luminaire is in operation, the more the light output decreases. CLO regulates the luminous flux and ensures constant light quality over the entire service life of the LED. This can increase the nominal output of the driver.


DALI stands for Digital Addressable Lighting Interface and is a system with which the luminaires can be individually controlled. For example, dimming can be controlled or sensors can be integrated. Another advantage of DALI lighting control systems is their energy efficiency. They can automatically adjust the light intensity to the time of day or daylight and the use of the room, which can contribute to considerable savings in electricity costs.


A diffuser is used to distribute light in a similar way to a lens optic. This consists of a material that allows daylight to pass through, such as polycarbonate or frosted glass. Glare can also be reduced with a light diffuser.

Emergency power

Optical radiation is absorbed in the skin layers and does not reach the inside of the body. One exception is the eye, which is transparent in a wavelength range of around 400 to 1400 nanometers. Radiation of this wavelength can reach the sensitive retina. Therefore, according to VDE, two organs must be protected against optical radiation: the skin and the eye. This is why the EN 62471 standard was developed. VDE test report for Lucid Arena: „The lamps/luminaires do not pose a hazard due to normal restrictions caused by user behavior“.

Energy efficiency class

Energy labels indicate the energy efficiency of the light. A stands for high energy efficiency, G for low energy efficiency (before 2021 still classified A+++ to D). Luminaires with lens optics or a beam angle <120 degrees beam angle can receive a better energy efficiency class despite the same energy efficiency.


HQI/HQL are still used in large numbers as luminaires in indoor areas.

HQI lamps are light sources with metal vapour technology – so-called metal vapor lamps (gas discharge lamps in which metal atoms are excited to glow by ionization in an electrical discharge).

Example: Halogen metal vapor lamps HQL are mercury vapor lamps (they are gas discharge lamps with mercury vapor filling).


  • with HQL lamps: use of toxic mercury and therefore problems with breakage and disposal
  • lower luminous efficacy with the older (mainly used) types service life of up to 30,000 hours (LED > 50,000 hours)
  • like almost all high-pressure lamps, need a few minutes to reach full light output


EU legislation: The sale of HQI and HQL with low luminous efficacy or with mercury has been banned by the EU. (Sale of fluorescent tubes ban from 2023) Commission Regulation (EC) No. 245/2009


IK is the impact resistance classification of a product. This indicates the mechanical load the luminaire must be able to withstand. The product must not splinter.

IK02 = 250 grams from 8 centimeters
IK04 = 250 grams from 20 centimeters
IK06 = 0.250 grams from 40 centimeters
IK08 = 2,000 grams from 25 centimeters
IK10 = 5,000 grams from 40 centimeters

Integrating sphere

The integrating sphere (Ulbrichtkugel, named after the engineer Richard Ulbricht) is a component of technical optics. It is used as a light source to achieve diffuse radiation from directed radiation or to collect radiation from highly divergent sources.

IP protection degree

In electrical engineering, protection classes are used to classify and label electrical equipment with regard to the safety measures in place to prevent electric shock. They also define the environment in which a luminaire can be used (e.g. damp rooms, outdoor areas, etc.). The IP protection class consists of two digits. The first digit describes the safety class with regard to contact and foreign bodies and the second digit describes the safety class with regard to water protection according to the following table:

First digit
Foreign body protection
Second digit
Water protection
IP 20
foreign body >12 mm
IP 23
foreign body >12 mm
spray water
IP 40
foreign body >1 mm
IP 44
foreign body >1 mm
splash water
IP 50
dust protected
IP 54
dust protected
splash water
IP 65
water jets
IP 66
strong water jets

Lights and light sources

A luminaire is an object that serves as lighting and has a fixture for a light source or contains a permanently installed light source (such as an LED module).

Light sources are all electrical equipment used to generate light and all objects that generate light through chemical or physical processes. They form a light source.

Example luminaire: Lucid arena pro

Example light source: Lucid PAR 58

Luminous efficacy

The luminous efficacy is the ratio between the luminous flux emitted (in lumens) and the energy consumed (= power consumed, in watts). The luminous efficacy is therefore given in: Lumen per watt. This value can be used to determine the energy efficiency class of a product.

Example of luminous efficacy:
Incandescent lamp: approx. 12 lumens/watt
Halogen lamp: 25 to 50 lumens/watt
Metal halide lamp: 50 to 117 lumens/watt
LED lights: 100 to 180 lumens/watt


Lumen is the unit of luminous flux. The luminous flux is the total amount of visible light that leaves a lamp. The sensitivity of the eye to the different wavelengths of light is also taken into account (by means of the so-called light sensitivity curve, the V-Lambda curve). The specification of luminous flux in lumens, for example, says nothing about how brightly a lamp can illuminate something, as the bundling of the light, for example, has no influence on the luminous flux – it only indicates how much light is generated in total and not in which direction it is emitted. The luminous flux is technically difficult to measure as the light emitted in all directions has to be added together. One way of doing this is the so-called „integrating sphere“.

LED service life

The LED service life indicates the service life in hours that can be expected from the LED. This does not refer to the service life of the entire luminaire, but only that of the LED chip.

The service life can also be influenced by external factors such as ambient temperature, fuse protection and mains voltage. The driver of the spotlight is also subject to the same factors and must be replaced once or twice during the LED service life. In order to define the LED service life even better, additional values such as L and B are used to further define the service life.

If, for example, the value L80 B10 is noted after the service life, this refers to the light output of the LED. 60,000 h L80 B10 means that 80 percent light output is still achieved after 60,000 hours and a maximum of 10 percent of the LEDs may fall below this value.

LED luminous flux / luminaire luminous flux - the difference

For many, lumens, or lumens per watt values, are the decisive factor when purchasing luminaires and calculating savings. However, there are major differences in the way they are communicated to customers. While the luminaire luminous flux indicates the actual lumens of the entire luminaire, the LED luminous flux only measures the pure LED chip without optics, glass or other covers. In this way, values far in excess of 200 lumens per watt can be achieved, which are nowhere near feasible in practical applications.

Depending on the material, beam angle, glare factor and quality of the optics, deviations between LED luminous flux and luminaire luminous flux of 50 percent can occur. Another point in terms of light efficiency is the warm and cold measurement of LEDs, and here too there are major differences in the way some manufacturers communicate with customers. In a warm measurement, for example, the LEDs are measured after an hour of being switched on, whereas in a cold measurement the LEDs are measured immediately after being switched on. The value of the cold measurement is much higher but not really practical. Differences in the lumen-per-watt ratio can also occur here. A difference in efficiency from warm to cold can often be 10 percent or more.

So don’t compare apples with oranges when buying, but ask about the two measured variables of efficiency at the moment of switch-on and after one hour of burning time.

At Lights 4 Europe, we have always been committed to transparency for our customers. For this reason, we have decided to communicate the luminaire luminous flux (cold) values in addition to our luminaire luminous flux (warm) and, above all, to explain them. In this way, we can protect our customers from the „lumen trap“ and ensure maximum transparency. Lights 4 Europe products comply with the measured values described. Cold values are expressly marked in our data sheets. If there is no explicit mention, you can assume practical values after one hour of burning.


Lux is the unit of illuminance. An illuminance of 1 lux results when a luminous flux of 1 lm (lumen) uniformly illuminates an area of 1 square meter. Illuminance indicates how brightly a surface is illuminated. The brightness sensitivity curve of the eye is also taken into account for illuminance. Illuminance can be easily measured with a luxmeter. In contrast to lumens, the lux value depends on the distance from the light source. If the distance from the light source is doubled, the illuminance drops to a quarter.

Examples of typical illuminance levels:
5 milliwatt laser pointer: 427,000 lux
Bright sunny day: 100,000 lux
Overcast summer day: 20,000 lux
Office/room lighting: 500 to 1,000 lux
Candle, about 1 meter away: 1 lux
Full moon night: 0.25 lux

MacAdam steps

MacAdam refers to the color tolerance (light color) of a product series. It is almost impossible to detect differences in class 1, even for highly sensitive measuring instruments. Even with McAdam 2 and 3, no differences can be perceived by the human eye. Only from a value of McAdam 4 or 5 can the human eye perceive color differences.

Maintenance factor

The maintenance factor is one of the most important parameters in the cost calculation when planning lighting. It takes into account the reduction in brightness over the service life of the luminaire. The lower the maintenance factor, the more additional luminaires need to be installed in a lighting system to achieve the required brightness.

Photobiological safety

Optical radiation is absorbed in the skin layers and does not reach the inside of the body. One exception is the eye, which is transparent in a wavelength range of around 400 to 1400 nanometers. Radiation of this wavelength can reach the sensitive retina. Therefore, according to VDE, two organs must be protected against optical radiation: the skin and the eye. This is why the EN 62471 standard was developed. VDE test report for Lucid Arena: „The lamps/luminaires do not pose a hazard due to normal restrictions caused by user behavior“.

Protection class

The protection class indicates which measures have been taken to prevent an electric shock.

Protection class 1: All electrically conductive housing parts are connected to the protective conductor (PE yellow/green).

Protection class 2: Reinforced or double insulation and electrically conductive surfaces are separated from live parts.

Protection class 3: Protection class 3 equipment operates with safety extra-low voltage and safety extra-low voltage.

Protection degree

In electrical engineering, the degree of protection is used to classify and label electrical equipment (e.g. luminaires) with regard to the safety measures in place to prevent electric shock. They therefore also define the environment in which a luminaire can be used (e.g. damp rooms, outdoor areas, . . .).

Sensors (OS-NET)

OS-NET is a type of wireless DALI network. These sensors can communicate with each other wirelessly via radio. They are programmed using a remote control. This technology makes it possible, for example, to implement daylight control with or without motion function – all in just one sensor! The ranges are 15m indoors and 100m outdoors.

Various luminaires can be used in a lighting project. A good example of this would be a production hall with adjoining high-bay racking. While one of our Linea continuous-row systems is used in the production area, Sirius 250 luminaires, for example, are installed in the high-bay warehouse.

This is where the OS-NET comes into play. Although two different lamp types with different sensors have been installed, they can easily be combined to form a group circuit.

The so-called OS-NET buttons offer an optional extension here. These can be installed anywhere and only require a 230V AC power supply. These can be used to switch the lamps (or the entire group in the case of a group circuit) on/off or dim them.

Service life

The period, specified in hours, that the LED can achieve. The LED service life depends on the ambient temperature, application, fuse protection and can be influenced by these.

Tc point

The Tc point indicates the warmest point of the luminaire. This is also the measuring point that is defined for the maximum surface temperature. This is particularly important for highly flammable surfaces or materials.


The UGR Unified Glare Rating is the measured variable for the glare of a specific environment. This is specified with values between 10 and 30, with 10 being the best and 30 the worst glare value.

Drawing and precision crafts UGR ≤ 16
Reading and writing activities, control activities, recommendation for offices UGR ≤ 19
Manual work in industry, reception UGR ≤ 22
Rough work, storage rooms UGR ≤ 25


Volt is the unit of measurement for electrical voltage.


Watt is a unit for electrically generated power. For electrical appliances, the maximum output is specified in watts.