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The ABC of Light

A lexicon of light and illumination


The ampere (A) is named after André Marie Ampère. It is the SI unit upon which electrical current intensity is based.


Every type of lighting has its own connector base. For example, every common light bulb (incandescent light bulb) has two types of screw threads, namely E 14 and E 27, which can be found on the light bulb type labels.

Burning position
The burning position determines at which angle, in reference to the horizontal, a lamp may be used. A lamp with a 360° burning position can be used universally. Lamps with 15° may only be used at the specified angle relative to the horizontal. Ignoring the burning position may lead to premature lamp failure.


see Light intensity

CE marking
The “CE” (Conseille de l’Europe) marking confirms that the manufacturer’s products comply with European regulations.

Coiled filament
This is also called a glowing filament or wire and indicates a tungsten wire twisted to a helix, which through resistance transforms electricity into light and heat. The resistance is notably less when turned on than it is during use, resulting in a higher current flow, which is why most light bulbs burn out when they are turned on.

Colour temperature
The colour of light measured in Kelvin units

Current capacity
see Ampere


A dimmer is a thyristor or triac AC switch used to regulate the brightness of light bulbs. Once a light is dimmed, it absorbs less power and subsequently uses less energy. This extends bulb life, in some cases remarkably, as the filament temperature is lowered. However, light efficiency is also profoundly diminished. Dimming also changes the light’s colour, the colour temperature sinks. Magnetic transformers use leading phase dimmers; electronic transformers use reverse phase control dimmers.


Electronic ballast or choke
This device is used to adapt the main voltage to the required lamp voltage, as well as to save energy. Electronic ballasts or chokes provide a smooth immediate start and lengthen lamp life.

Electronic transformers
Electronic transformers are constructed as switch mode power supplies which are noted for their minimal weight and diminutive size. The advantages are an independent output voltage, just under 12 v, optimal for halogen lamps; a soft start and an overload protection.
Their application is limited to approximately <200 volt-ampere due to the high spark protection, which is required for the increased output and a contact performance of 30 to 40 kHz. Lamps equipped with electronic transformers must undergo an EMC inspection. For failure protection reasons, the maximum secondary cable distance to the furthest lamp may not exceed 2 meters. 

Emitted light
Defines the amount of illumination radiated by a light source.  

The electromagnetic compatibility (EMC) denotes the standard optimal condition of technical devices, which avoids mutually negative influences incurred by undesired electrical or electronic effects.

Energy efficiency
This tells us how much electricity in relationship to light output a light source consumes on a scale from A to G. A is highly efficient; B to G consume more electricity.

Energy-saving lighting
see fluorescent lighting

This is the main guideline by which lamps are to be tested.

Energy efficiency classification
The energy efficiency classification determines the power consumption of a given device. There are seven classes ranging from A++ for very efficient, to “E” for a low efficiency performance.   

Energy-saving lighting 

EU Energy label
The EU Energy label conveys to consumers the energy efficiency level of light bulbs of a given lamp as well as the compatibility bulb types and lamps


Fluorescent lighting (energy-saving lamps)
Energy-saving lamps are principally compact fluorescent lamps with an integrated electronic ballast and an Edison base (screw base) so they can be used instead of common light bulbs. The term, however, is technologically neutral and can apply to other energy-saving lighting. Energy-saving lamps transform 30% to 40% of energy into light. The rest is lost to heat. Energy-saving, fluorescent lighting tubes have less gaseous discharge compared to other fluorescent lamps and they are curved or in multiple folds to save space, ergo the prefix "compact".

see Hertz 


GS certification
The GS seal certifies that products comply with all device and product safety laws.


Halogen lamps
Halogen lamps work with a coil similar to normal light bulbs, albeit at a somewhat higher coil temperature. The internal halogen gases hinder the metal gases exuding from the coil to condense on the bulb interior, causing it to blacken. When illuminated, the tungsten emitting from the coil by way of diffusion or convection near the glass bulb wall reaches temperatures of <1400° Kelvin in which stable halogen compounds occur. Thermal flow brings these compounds back close to the coil, where they disintegrate. A part of the tungsten is transported back to the coil, but not to the point from which it was generated. This process creates a higher efficiency and longer life in comparison to common light bulbs. The average lifespan of halogen lamps has been registered at 2000 hours.

Hertz (Hz)
This is the SI unit for frequency. The unit is named for the German physicist Heinrich Rudolf Hertz. Hertz units indicate the number of vibrations per second, or more generally, the number of any repetitive action per second.

High-volt halogen lamps
These come in a variety of models. Most common are the halogen glow sticks performing at 100 W to 500 W or more. The newer halogen lamps have lower wattage and can even be mounted in conventional lamp sockets.  This is a good alternative to conventional light bulbs. At the same time, high-volt, cold-light lamps with GZ-10 sockets are being introduced, which are similar to the low-volt Cool beam lighting. High-volt halogen lamps are compatible with conventional leading phase dimmers.

High-volt technology
These lamps do not require a transformer, as they run on line voltage (230 volts in Germany).


Illumination intensity
Illumination intensity is the light radiation per surface unit measured in lux (lx) units, 1 lumen per square meter = 1 lux.

Illumination intensity determines how brightly objects are illuminated. Whether the light is enough for us to recognize easily the object, however, is not dependent on the illumination intensity, but on the amount of light, the object reflects back to our eyes.

Illumination intensity diminishes by the distance to the light source squared, i.e. double distance = 4 times less illumination intensity. The illumination intensity of daylight (noon) fluctuates between 100,000 lx on a clear summer day and 400 lx on a cloudy winter day.

Incandescent light bulb
Light bulbs are typical thermal radiators in which a filament set into a vacuum bulb  or into an inert gas atmosphere is heated by electrical current to approximately  2600-3000 Kelvin, causing illumination. The main part of the emitted radiation lies within the infrared area. 

Only 5% to 10% of the energy in a light bulb is transformed into light, the rest is lost to heat.

IP protection class The protection type determines the appropriateness of electrical operating resources (for example, lighting) for varying environs, calculating the external influences to which lighting may be subject. For example, outdoor or bath lighting requires higher protection against moisture or splatter penetration. IP categories determine the level of protection. The higher the number, the better the protection.




A lamp is the illuminant which is installed in a lighting.

Lamp current
Is the current, in ampere or milliampere, a lamp or lighting draws. For example, a lighting with a 60 W light bulb draws 60 W/230 V = 261 mA. 

A Light Emitting Diode (LED) is an electronic semi-conductor building component. When electricity flows through the diode forward-bias, the diode radiates light at a frequency relative to the semi-conductor material.  Depending on where LEDs are applied, they can attain a life of 80,000 to 100,000 hours. Since LEDs release hardly any energy in the form of warmth and UV rays, they are much more efficient than light bulbs.

LED technology
The most efficient white LEDs attain a light efficiency of 40 to 100 lm/W (November 2007). This is far more than that of light bulbs or halogen lamps with, respectively, 17 or 30 lm/W and reaches the efficiency of fluorescent lamps, with their 60–110 lm/W.  Only recently has this lighting technology found its way into household use. LED lighting is now available in varying base forms.

Light flux
Light flux, measured in lumen (lm), is the entire radiance a light source renders in all directions. This is an important factor in calculating energy efficiency.  

Light intensity
The luminous flux intensity, in which a point source of light radiates in one particular direction, is the light intensity. This is measured in Candela (cd), the luminous power of a light source radiating within an infinitely tiny solid angle. A Christmas candle radiating light evenly in all directions has a light intensity of 1 cd. If the light is focused with a reflector, the solid angle narrows and the light intensity increases.  

Lighting is any object serving the purpose of illumination and equipped with a lamp receptacle or contains a permanently installed illuminant.

Low-volt technology
In contrast to high-volt technology, low-volt technology requires a transformer to transform the supply voltage from 230 volts (in Germany) to 12 volts of operating voltage. 

see Light flux 

Luminance is the photometric measurement for brightness. A light source appears brighter the smaller its surface is in relationship to light intensity I. Luminance is what people perceive as brightness.  


Mercury is a chemical element and so-called transitional metal, usually fluid in form. Its original use in thermometers has been banned since 2009. Today, mercury can be found in energy-saving lamps. When such lamps break, the mercury can escape. An operating lamp has a higher proportion of mercury gas than a cold one. If an energy-saving breaks, air out the room thoroughly and be sure you have no contact with mercury when tidying up. A summary of all safety measures can be found here.

Moisture-proof lamp
Moisture-proof lamps carry at least the protection class IP 44 stamp and are predominantly for use in baths or gardens. The protection class number indicates to which extent the lamp is protected against moisture and dirt penetration.


Neon lamps
Neon tubes are lighting tubes filled with the noble gas neon and shine deep red when subjected to several 100 to 1,000 volts. Neon tubes are not fluorescent lamps, as they work with neon filling and shine reddish orange. Fluorescent lamps contain mercury, and have a luminescent substance on the inside of the glass. Neon tubes, however, are not coated, but clear or tinted red. Neon tubes are used in (luminous) advertising and as beacons for high structures.    





RGB (red/green/blue)
Installing colour changers provides a variety of coloured lights.


SI unit
The International System of Units (Système international d’unités in French) is the most broadly accepted unit system of physical quantities.  

see Base

Switching cycle
This is a factor in a lamp’s life expectancy. A switching cycle encompasses the switch from on to off and back again, or vice versa.


A transformer is an electro-technical operating resource, serving primarily the transferral of electrical energy to another electrical voltage level.  The current intensity relationship on the input and output terminals is reverse to the relationship of the voltage level measured there (when one ignores the losses).

A transformer contains at least one spool with several tapping points, or two or more separate spools which are inductively, i.e. magnetically coupled. Practical transformer models generally house their spools on a mutual iron or ferrite core to generate an optimal magnetic flow in the transformer core as well as to maximise the spools’ magnetic cross-coupling.


UV rays
In addition to visible light, the spectrum also contains a long and short wave area, which is invisible to the human eye. Shortwave ultra-violet rays are harmful to the eye, especially UV-B and UV-C rays. Halogen light radiates in a particularly broad spectrum, including the UV areas, where UV rays are eliminated via a filter.


A volt (V) is the derivative SI unit of electrical tension. The volt is named for the Italian physicist Alessandro Volta.

see Volt

VDE – Verband Deutscher Elektrotechniker (Association of German Electrical Engineers)
The VDE is an industrial and professional organization. It documents the safety and standards conformity of electrical products in view to their electrical, mechanical, thermal and related risks. Thus, many lamps carry the VDE stamp. The VDE also awards the European safety-tested mark ENEC. 


A watt is the SI unit of capacity in Physics and is named after the Scottish inventor James Watt.
Watt is the product of current intensity and electrical voltage, for example 230 V x 0.5 A =115 W




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