What does a zero watt lamp indicate

Lamps, Lumen, Lux, Watt and Kelvin
Brief information on the lighting chaos

In 2009 the EU decided to phase out "inefficient" light sources (lamps). Therefore, after the 100 W and 75 W incandescent lamps, the 60 W incandescent lamps also disappeared from the shelves on September 1, 2011. A multitude of alternative techniques are being used in place of the incandescent lamp. So lightbulbs are bad, halogen lamps a little less bad, energy-saving lamps sometimes bad sometimes good and LED lights are always good - or how or what? With the new lamps, the wattage no longer says anything about their brightness. Other parameters are intended to make orientation easier for the consumer.

It's not that simple. It starts with the fact that energy-saving lamps are actually fluorescent lamps, more precisely compact fluorescent lamps. Therefore, we should begin with an overview of the various lighting fixtures. By the way: The specialist describes the pure lighting fixtures as "lamps" or "illuminants", whereas the surrounding area with the base, socket and lampshade is called "luminaire". The "lampshade" should therefore actually also be called "lampshade".

Lamp types

The Lightbulb is one of the oldest electrical light sources. It was invented in 1854 by the German watchmaker Heinrich Goebel and further developed by Edison in 1879 into a light bulb ready for production. The incandescent lamp is a so-called temperature radiator. Inside, an electric current makes a coiled tungsten wire glow. Only about 5% of the energy is converted into light, the rest warms the room. An incandescent lamp has a lifespan of approx. 1000 hours.

The addition of halogens turns the normal incandescent lamp into a Halogen light bulb. The halogens capture the tungsten atoms evaporated from the filament and transport them back to it. Halogen light bulbs are up to 50% brighter and last around twice as long as conventional light bulbs. They are also usually much smaller and produce brilliant light that is whiter than that of the incandescent lamp. The most common are those Low voltage-Versions that are particularly small and economical. However, they need a transformer or ballast that reduces the mains voltage to 12 volts. Halogen lamps in High voltageTechnology serve as a direct replacement for conventional incandescent lamps.

Fluorescent lamps generate around 70% of the world's artificial light. They are commonly referred to as "neon tubes", although a neon fill alone would produce a deep red light. An electrical discharge between the two electrodes of the glass tube generates barely visible UV radiation, which is converted into light by phosphors on the inside of the glass bulb. Fluorescent lamps only need a fifth of the current of an incandescent lamp with the same brightness and their lifespan is more than 12,000 hours. Fluorescent lamps require a "starter" which, when switched on, heats up the two electrodes in order to initiate the discharge. In order to limit the current during operation, a choke coil used to be connected upstream; today, electronic ballasts are used.

The Energy saving lamp generates light based on the same principle as fluorescent lamps. By folding and rolling up the glass tube, these lamps are built very compact → compact fluorescent lamps. The required ballast is integrated in the base, sometimes also in the luminaire. This saves up to 80% electricity and compared to incandescent lamps, energy-saving lamps have a significantly longer burn time. Modern high-quality energy-saving lamps last about 15000h. An incandescent lamp has a lifespan of around 1000 hours. The lighting in stairwells and corridors requires lamps with a high switching resistance, otherwise the service life drops rapidly. Lamps that are used in stairwells, for example, have to get bright quickly. The start-up time of each lamp (usually the time it takes for the lamp to switch on until it reaches 60% of the specified luminous flux) is stated on the packaging. Their higher weight must be taken into account as well as the light spectrum that differs from that of the light bulb. Energy-saving lamps also contain traces of mercury.
From my point of view, the energy-saving lamp is a transitional model that will sooner or later be replaced by LED light sources. The main reasons for this are that the compact fluorescent lamps do not really fit into the older luminaires (especially if the lamp is visible) - they look too clunky in the base and a plastic cover, which is supposed to create a certain similarity to incandescent lamps, does not really help . There are also still lamps that only reach their final brightness after several minutes (so you leave them on if you need light again later and the savings effect is with the devil). In addition, the service life of many lamps does not keep what was promised - especially if they are switched on and off frequently.

LED lamps and light emitting diodes are becoming more and more popular as a means of lighting, as new and brighter LED lamps appear on the market almost every day. White light-emitting diodes as LED lamps and LED lights are also becoming increasingly popular because they consume very little electricity. The service life of the lamps is unsurpassed - if installed correctly, the lamps will last up to 50 years, although the brightness will decrease over the years.
The LED offers the opportunity to design completely new lights, because the freedom of the designer is almost infinite with this light source. Initially (2010/2011) mainly LED light sources appeared, which look like classic light bulbs, but were also quite bulky. Here many small light-emitting diodes are put together in a common socket. Some (cheap) models therefore look more like a corn cob than a light bulb. In the meantime, however, there are LED light sources that not only look appealing, but can also replace the old light bulb well - both in terms of luminance and color. The service life is also much longer than the guarantee period. When installing LED light sources, however, keep in mind that they won't last forever either.
Unfortunately, there is more to LED light sources than just the wattage. Which initially throws us into confusion (some of the terms are taken up again below). Here are some recommendations:

  • Light color: 2700 - 3000 Kelvin (the higher the value, the more bluish, 6000 Kelvin is bright blue)
  • Color fastness: RA90 - RA80 (the higher the better, the sun has RA100)
  • Brightness: 800 lumens or more (rule of thumb: lumens / 12 roughly corresponds to the watts of the old light bulb).
  • Power consumption: around 10 watts (depends on the brightness)
  • Brightness / power consumption: 80 lumens per watt or more.
  • Beam angle: 270 ° is very good, 180 ° is satisfactory.
If the information is not on the box, caution should be exercised. The LEDs should also not be visible ("corn cobs"), without a diffuser you can see individual points of light. Even if the box says Lux instead of Lumen, you should be suspicious.
Another aspect of LED light sources is the operating temperature. Since the light is generated on a much smaller area than with other lamps, the heating tends to occur selectively → the heat is more difficult to dissipate (recognizable by the cooling fins on the lamp base). All manufacturers also specify the maximum operating temperature. In many luminaires, however, there is no ventilation, especially in the base area. If the LED lamp overheats, it does not break immediately, but its service life drops rapidly. In this respect, LED light sources are not suitable for every application.

The Mercury vapor lamp is a gas discharge lamp which, in addition to mercury, which is partially gaseous due to the low vapor pressure even at room temperature, also contains a noble gas (usually argon) to facilitate ignition. It was invented in 1892 by the Berlin physicist Martin Leo Arons. The earlier lamps produced a blue-green light, now they are also available with a more white light.
Low pressure lamps (internal pressure up to about 10 mbar) have a large proportion of ultraviolet radiation; they are suitable as so-called quartz lamps (lamp bulbs made of quartz glass) as an ultraviolet source. They have a high luminous efficacy and a long service life. Except for lamps for solariums, disinfection, etc., UV emission is prevented with special types of glass.
Medium pressure lamps are used in industry to cure special UV-reactive paints, adhesives and printing inks.
High pressure mercury vapor lamps have operating pressures of up to around 10 bar and are often used for street and industrial lighting. You need a ballast. These lamps have a good luminous efficacy and a blue-green light color.
Ultra-high pressure lamps have an operating pressure of up to 100 bar, but this only builds up slowly after ignition. They have a very high luminance, are made of thick silica glass without an additional bulb and serve as an intense ultraviolet source in photolithography, among other things. In addition to mercury, high pressure lamps are also offered filled with xenon and are used as light sources in vehicle headlights and cinema projectors.

Sodium vapor lamps are available in low and high pressure versions. In addition to neon, a low-pressure sodium vapor lamp also contains sodium vapor. This lamp shape has a very high light output (up to 183 lm / W). They emit an intense yellow light and therefore have poor color rendering. Their lifespan is very long, it is approx. 7500 hours.
In contrast, high-pressure sodium vapor lamps have a broader color spectrum. They deliver all body colors, but this leads to a lower light yield (up to 130 lm / W). Sodium vapor lamps are often used to illuminate pedestrian crossings, traffic junctions, port or industrial facilities, as the yellow light makes outlines easier to see.

With the currently (mid-2014) most common lighting fixtures, it can be seen that even the still quite expensive LED lamps pay for themselves due to their low power consumption and long service life. After about 2000 hours of burning, the LED has overtaken the good old light bulb (source: Bavarian State Office for the Environment):

Light spectrum and color

Light is a form of energy that occurs as electromagnetic radiation and is closely related to other types of electromagnetic radiation, such as radio waves, infrared and ultraviolet radiation, X-rays. Light is that small part of electromagnetic radiation that the eye can perceive. This visible radiation creates a sensation of light and color in the eye. The only difference between the different types of radiation is the wavelength.

Rays with a wavelength between 380 nm and 780 nm form the visible part of the electromagnetic spectrum, which is why they are called light. The eye perceives different wavelengths within this range as colors. A certain color impression belongs to each wavelength. The spectrum of sunlight shows a continuous transition from short-wave ultraviolet through violet, blue, blue-green, green, green-yellow, orange to long-wave red. Our eye has its maximum sensitivity at a wavelength of 555 nm (yellow-green). White light is a mixture of visible wavelengths, which can be shown with a prism. The white light is split up into its color components, its spectrum.

The following illustration shows typical spectra of daylight, incandescent lamp, fluorescent lamp and LED lighting. As you can see, the energy-saving lamps do not have a continuous spectrum, but only emit in a few "bands".

Humans experience their environment not only as light and dark, light and shadow, but also through colors. A colored surface appears colored because it does not reflect all wavelengths, but only certain ones. In the case of blue color, a high proportion of blue color components is reflected in the spectrum of light and few or no yellow or red color components at all. However, an object painted blue only appears blue if the light falling on it contains a sufficient proportion of blue radiation that can be reflected. On the other hand, such an object appears dark if the light source does not contain any blue components.

Although two light sources can appear the same in terms of color, not all of the colored surfaces illuminated by them have to look the same. Because two light sources that appear to be the same white can be created by combining different wavelengths. And since a surface does not necessarily reflect the wavelengths of the lamps to the same extent, the color impression changes. That is why the lamp spectra play a role and not just the light color.

The light emitted by lamps has its own color, the so-called light color. It is determined by the color temperature in Kelvin (K). The higher the temperature, the whiter the light color. The Color temperature (light color) is measured in Kelvin. Warm light is suitable for areas that should exude a cozy atmosphere, e.g. B. in the living room. Lamps with a value of 2500K (extra warm white) to 2700K (warm white) are suitable for this. Values ​​from 4000K (neutral white) to 6500K (daylight white) are suitable for a room with a businesslike atmosphere such as a kitchen, hallway or study. The light from lamps of the same light color can have different color rendering properties. The reason for this is the different spectral composition of the light color. It is therefore not possible to draw conclusions about the quality of its color rendering from the light color of a lamp.

The color temperature of the color of a light source is determined by comparison with the color of a "black body". This is a relatively idealized body without reflection radiation. He completely swallows the light falling on him. If it is slowly heated, it runs through a color scale from dark red to orange, yellow and white to light blue. The higher the temperature, the whiter the color.

The color temperature indicates the color shift (reddish-yellow to bluish-white) of a light source. It says nothing about the quality of the light. This is called the color rendering index, which indicates the accuracy of the color rendering. This in turn depends on the color spectrum.

The warm light of the light bulb corresponds to approx. 2700 Kelvin, that of the halogen lamp approx. 3200 Kelvin. With the energy-saving lamp, values ​​of 2000 to 10000 Kelvin can be achieved, depending on the composition of the phosphors used. In contrast to light bulbs, such lamps have a discontinuous line spectrum, which means that color components are missing and so not all colors can be reproduced correctly. With the Color rendering index Ra (CRI) the color rendering accuracy of lamps can be specified. The color rendering of a lamp indicates the quality of the rendering of 8 reference colors when illuminated with this lamp (DIN 6169 defines 14 colors in total). The reproduction of pastel colors is checked, but not that of saturated colors.

The Ra scale goes up to a maximum of 100:

  • Ra = 90 ... 100 Excellent color rendering properties
  • Ra = 80 ... 90 Good color rendering properties
  • Ra = 60 ... 80 Medium color rendering properties
  • Ra <60 Poor color rendering properties
For common requirements in the industrial and private sector, an Ra greater than 80 is usually sufficient. In contrast, the arts and museums, for example, have higher demands. Here the Ra value should be more than 90 with a focus on a very high quality of light. The maximum possible Ra is 100, which is achieved, among other things, by incandescent lamps. Please note, however, that there are also many situations in which it is not so much the exact and natural color rendering of the lighting that is important, but rather the lighting level and the light output. Warm white, for example, creates a cozy, inviting atmosphere, on the other hand, neutral white creates a matter-of-fact, business atmosphere.

The following table shows the average values ​​of color temperature and color rendering index.

lamp Color temperatureIndex Ra
Lightbulb 2700 K100
Halogen lamp 2900 K100
Energy saving lamp 2500 K80
LED 3000 K90
Fluorescent tube 4000 K60 - 90

Sunlight has a color temperature between 5000 K and 6500 K, whereas the moon only brings it to around 4000 K.

The following pictograms on the packaging provide information about the light color (example Osram):

The color rendering of compact fluorescent lamps and fluorescent tubes is marked with an internationally valid light color number, for example an energy-saving lamp with the designation "827" is extra warm white. The first digit denotes the color rendering level, which is determined by the color rendering index Ra:

4 = color rendering level 1B (Ra 40 - 49)
5 = color rendering level 1B (Ra 50 - 59)
6 = color rendering level 1B (Ra 60 - 69)
7 = color rendering level 1B (Ra 70 - 79)
8 = color rendering level 1B (Ra 80 - 89)
9 = color rendering level 1A (Ra> 90)

The second and third numbers indicate the color temperature in Kelvin:

827 = extra warm white 2700 K
830 = warm white 3000 K
840 = neutral white 4000 K
860 = daylight white 6000 K

Watts, lumens, lux, candela?

When the first incandescent lamps appeared at the end of the 19th century, their luminous efficacy1) was just 3 lm / W (lumens per watt). With today's high-voltage incandescent lamps, it is around 14 lm / W. In the middle of the last century, the gas discharge and fluorescent lamps increased the luminous efficacy to approx. 30 to 35 lm / W and fluorescent lamps with luminous efficacies of up to 100 lm / W are still the most economical light sources.

In the good, old incandescent lamp, the electric current flows through a thin, high-resistance tungsten filament (filament), whereby the filament is heated to embers. To protect the filament from oxidation, it is either placed in an evacuated glass flask or a flask filled with gas (usually a mixture of nitrogen and argon). The evaporation of the tungsten atoms of the filament leads to blackening of the inside of the bulb and makes the filament thinner until it breaks at its weakest point and the lamp "burns out". Incidentally, the industry soon artificially limited the life of an incandescent lamp to around 1000 hours. The Centennial Light ("Centennial Light") is an exception; it is considered to be the longest-lasting incandescent lamp in the world. It is located in the fire station in the city of Livermore near San Francisco in the US state of California (de.wikipedia.org/wiki/Centennial_Light).

By using a compact quartz glass bulb and adding a halogen (iodine, formerly also bromine), incandescent lamps can be constructed that have a service life of 2000 to 5000 hours even at elevated operating temperatures of 2800 to 3100 K. These "halogen incandescent lamps" have a whiter light and higher luminous efficacy compared to conventional incandescent lamps. The halogen reacts with the tungsten atoms evaporated from the filament and stabilizes an atmosphere containing tungsten. At high temperatures the compound breaks down again into halogen and tungsten. The latter is reflected on the filament. The addition of halogen prevents the precipitation of tungsten on the glass bulb. Therefore, the glass bulb of a halogen lamp can be made very compact.

The fluorescent or compact fluorescent lamps are in principle a low-pressure mercury vapor gas discharge lamp. In these gas discharge lamps, the electric current flows through a gas between the two electrodes, which are attached to the ends of a closed glass tube. The collisions of free electrons and gas atoms excite the gas atoms and raise them to a higher energy level. These excited atoms then fall back to their natural energy level and give off the excess energy in the form of radiation. The inside of the fluorescent lamp is coated with a mixture of phosphors (also called phosphors) in order to convert the invisible ultraviolet radiation produced by the discharge of the mercury vapor into light. Since there is a wide variety of phosphors, the lamps are available in many variations of light colors.

Oh, the times were easy when you just bought a 40 watt light bulb. In the case of the "new" light sources, the wattage rating is no longer used. In the case of energy-saving lamps, the (relatively imprecise) donkey bridge "Incandescent lamp watts through five gives energy-saving lamp watts" helped. However, it was only of limited use and does not help with halogen and LED lamps.

Therefore, the following information will be found on lamp packaging in the future:

  • Watt (W): the well-known watt specification shows the electrical power consumption, i.e. the power consumption
  • Lumen (lm): this value for the luminous flux indicates how bright a lamp is
  • Comparative value: which classic incandescent lamp the lamp corresponds to (in W)
  • Lifespan: Specified in hours and years (with three hours of operation per day)
  • Switching cycles: how often can a lamp be switched on and off without being damaged
  • Light color: value for the color temperature with the unit Kelvin (K), see above
  • Color rendering index Ra: (voluntary) how faithfully the light from the lamp reproduces the colors of the illuminated objects.
But, as I said, this is still a long way off. In the meantime, you still have to grapple with performance data such as LUX, Lumen and Candela. And if you want to build your own lamp from individual LEDs, you only have this information and no comparison value. The following overview explains briefly what these terms mean. For all dimensions, the higher the value of the specification, the brighter the lamp.

Lumen [lm] - luminous flux

Lumen is the unit of luminous flux. It describes the power emitted per second in the wave range of visible light. As a photometric unit, the lumen takes into account the sensitivity of the human eye: two identical light sources are perceived as equally bright if they emit the same luminous flux (regardless of color). 1 lumen is defined as the luminous flux of a 1.464 mW, 555 nm light source with 100% efficiency. A 1.464 mW strong red light source delivers only about 0.1 lm, since the eye only has 10% of its maximum sensitivity in the red. Some comparative information:
  • A 60 watt incandescent lamp has a luminous flux of 600 lm
  • A 100 watt incandescent lamp has a luminous flux of 1500 lm
  • A 40 watt fluorescent tube has a luminous flux of 2300 lm
  • A 100 watt mercury vapor lamp has a luminous flux of 4500 lm
  • A 2 kW metal halide lamp has a luminous flux of 200,000 lm
With "ANSI Lumen" the luminous flux z. B. a projector measured on the screen. With this standardized measuring method, the illuminance is measured on a screen with nine fields and the mean value of the illuminance of all nine fields is determined. The mean value multiplied by the projection area results in the ANSI lumens. So you can compare different projectors and lamp types with each other. However, the relevant standard was withdrawn by ANSI in 2003 and is no longer there. On the other hand, the practically identical IEC and DIN standards apply. The information provided by most projector manufacturers relates to the maximum settings that conform to standards, which are rarely optimal in practice. The luminous fluxes achieved with the optimal setting are sometimes significantly lower.

Candela [cd] - luminous intensity

Candela (Latin for sebum, wax light) measures the luminous flux that is emitted in a certain solid angle, measured at a great distance from the light source. A candle corresponds to a light intensity of 1 candela (cd), a 100 watt incandescent lamp a light intensity of approx. 110 cd and a 40 watt fluorescent lamp approx. 180 cd. Information on the luminous intensity can usually be found in the case of bundled light sources such as halogen reflector lamps or LEDs. Together with the light intensity, an opening angle is then often given, which indicates how large the angle of the light cone is at the edge of which the light intensity has dropped to half. Lasers achieve extreme light intensity because the light beam they emit has a very small opening angle. The comparison of light sources is made more difficult by the fact that information about luminous flux and luminous intensity is given and the color of the light may also have to be taken into account. Examples:
  • 5 W bicycle lamp without reflector: 2.5 cd
  • 5 W bicycle lamp with reflector: 250 cd
  • 120 W reflector bulb: 10,000 cd

Lux [lx] - illuminance

Lux is the SI unit of illuminance and measures the luminous flux that hits a certain surface at a receiver. So it is measured how much light actually z. B. arrives on your desk - regardless of the lumen indication on the light source. Compliance with standards and guidelines is based on this. 1 lux = 1 lumen / m2 The illuminance on an object decreases with the square of the distance to the light source.

Sunlight at noon in summer corresponds approximately to an illuminance of 100,000 lux and an overcast sky in summer about 10,000 to 20,000 lux. Artificial light in a well-lit office has about 500 lux. The following table lists some typical values:

Light situationIlluminance
Sun, clear sky100,000 lx
Sun, overcast sky20,000 lx
Summer in the shade10,000 lx
TV studio lighting1,000 lx
Office lighting500 lx
Corridor lighting100 lx
Street lighting10 lx
Candle 1 m away1 lx
Full moon with a clear sky0.25 lx
starry night sky0.001 lx
cloudy night sky0.0001 lx

According to EN 12464-1, the following applies to the illuminance in offices:

Task or activityLighting
strength [lx]
Filing, copying, etc.≥ 300
Write, type, read≥ 500
Technical drawing≥ 750
CAD workplaces≥ 500
Conference rooms≥ 500

The conversion of lumens, candela and lux is based on the following formulas:

The luminous intensity (candela, cd) results from the luminous flux (lumen, lm) divided by the solid angle (steradian, sr):

Luminous intensity (cd) = luminous flux (lm) / solid angle (sr) The illuminance (lux, lx) results from the luminous intensity (candela, cd) divided by the square of the radius or the distance of the illuminated area: Illuminance (lx) = luminous intensity ( cd) / r2 The illuminated (circular) area can be calculated from the radiation angle and the distance to the light source: Area = solid angle * distance2 Solid angle (steradian, sterad, sr) is understood to mean the ratio of the part of a spherical surface that a cone, starting at a certain acute angle from the center of the sphere, cuts to the square of the spherical radius. In order to get to the illuminated area, the solid angle sr of the radiation angle must be determined: sr = 4 * Pi * (sin (radiation angle / 4))2
Beam angleSolid angle srBeam angleSolid angle sr

This can then be used to calculate the light intensity and the illuminance.

Here is an example from practice: An LED spotlight with 400 lumens, a beam angle of 35 ° and a distance of 2.40 m to the floor creates an illuminated area of ​​approx. 1.25 square meters, a light intensity of 1375 candela and an illuminance of approx. 240 lux.


The luminance indicates which luminous flux is emitted or reflected from a certain surface in a certain direction (cd / m2). It is the measure of the impression of brightness that an illuminated / self-luminous object creates in the human eye. Luminance = light intensity / area
  • Surface of the sun: 1,650,000,000 cd / m2
  • Filament of a clear incandescent lamp: 7,000,000 cd / m2
  • Fluorescent lamp: 5000 - 15,000 cd / m2

You can get help with converting candela to lumen on the website www.settleback.de/applets/candela-to-lumen/.

Power [W]

This is the electrical power consumed by the lamp (unit watt). Due to the vastly different degrees of efficiency of light sources, it is impossible to compare them only on the basis of the power consumed (unit watt). Therefore, lamps are better compared based on the amount of light emitted (unit lumen). In the case of lamps that are equipped with electronic ballasts and are operated as a complete system, it is common to use the power consumed electrically by the system. A poor degree of efficiency in the ballast therefore reduces the light yield of the system.

Furthermore, the efficiencies of the lamps can be easily compared using the lumen / watt division. For example, a 75 W lamp has approx. 900 lumens, i.e. approx. 12 lm / W, an energy-saving lamp of roughly the same brightness has 11 W power consumption, i.e. approx. 82 lm / W.

The following table shows some typical lighting fixtures in comparison.

Light sourceEl. Power watt)Luminous flux (lumens)Luminous efficacy (lm / W)
Fluorescent lamp58540090
Sodium low pressure13026000200
Hg high pressure10005800058
Halogen reflector 10 degrees50--
Halogen reflector 60 degrees50--
Luxeon LED11818

Luminous efficiency in lm / W, switch-on time, service life, disposal

TypeLight output [lm / W]Switch-on timeService life [h]disposal
Lightbulb5 - 16 lm / Wright away1,000 hresidual waste
HV halogen 220 V14 - 25 lm / Wright away2,000 hresidual waste
LV halogen 12 V14 - 25 lm / Wright away2,000 hresidual waste
Energy saving lamp ESL35 - 75 lm / Wmedium10,000 hRecycling center
Fluorescent lamps T8 L50 - 105 lm / Wfast20,000 hRecycling center
Fluorescent lamps T5 L50 - 105 lm / Wfast20,000 hRecycling center
led Lamps10 - 100 lm \ Wright away50,000 hRecycling center

Comparison table

The following table is intended to facilitate the comparison between the currently available lamp types. Often, "crooked" lumen values ​​are also printed on the packaging - depending on the performance of the respective product. In this respect, the table can only provide guidelines (as of the end of 2011). With LED light bodies, the light output increases steadily due to new developments with the same power consumption. There are already replacements for T8 fluorescent tubes with 100 lm / W.
Amount of light [lm]Incandescent lamp [W]LV halogen [W]HV halogen [W]ESL [W]T8 L [W]T5 L [W]LED [W]
100 15 10  3   2
200 25   5   3,7
300  20 25   66,5
400 40   7  88
500   40     
600  35  11   9
700 60       
800  50 60    12
900 75   15 15 13 
1000       15-17
1200    20 1614 
1300     18  
1400 100 75      
1500   100 23    
2000 150 100      
2500   150  3028 
3000 200    36 35 
5000   300  58 54 
10000   500     
20000   1000     
40000   2000     
ESL = energy saving lamp
T8 L = 26 mm (8/8 inch) T8 fluorescent lamp
T5 L = 16 mm (5/8 inch) T5 fluorescent lamp

The following graphic from the Bavarian State Office for the Environment may help you to get a quick overview. Here you can roughly estimate what power you need for an "incandescent lamp equivalent":

Energy label for lamps

Since September 1st, 2013 there has been a new labeling requirement for lamps. The previous type of classification remains the same: It starts with the best efficiency with the letter A, and so there is actually no space for products that use energy even more economically. The EU has also used the crutch of the efficiency classes A + and A ++ already known from household appliances here. These now identify the particularly energy-efficient products. In return, the lowest energy efficiency classes F and G will no longer apply. From now on, almost all light sources must be labeled. Previously, lamps with directional light, e.g. B. reflector lamps, excepted. In addition to the efficiency class, the label will in future also provide information on electricity consumption in kWh per 1000 hours of operation.
Lamps and LED modules with a luminous flux of less than 30 lm, battery-operated lamps and lamps whose primary purpose is not lighting (e.g. photo flash lamps) do not have to be labeled. Furthermore, the following technical data of the lamps must be stated on the packaging:
  • Luminous flux in lm
  • Power consumption in W
  • Comparative value in W (output of a comparable classic incandescent lamp)
  • Lifespan in hours and years (with three hours of operation per day)
  • Switching cycles
  • Light color in K (e.g. warm white = 2700 K)
  • Start-up time (time until a lamp has reached 60% of its final brightness)
  • Suitability for dimmers
  • Length and diameter in mm
  • Mercury content
The requirements of class A ++ are currently only met by a few LED light sources and individual high-pressure discharge lamps. Class A + has very good LED modules, very efficient compact fluorescent lamps (energy-saving lamps) and high-pressure discharge lamps. The majority of LED lamps, energy-saving lamps and fluorescent lamps are only class A. Low-voltage halogen lamps, due to their lamp technology, can only achieve energy label B - but then they have to be very economical. High-voltage halogen lamps for mains voltage occupy classes C and D. Conventional incandescent lamps achieve the highest class E or F, if you can still get them.

The following infographic (source: Bavarian State Office for the Environment) summarizes the most important properties of the lamps (status: end of 2013). Personally, I see energy-saving lamps as a temporary solution that will disappear in the not too distant future.

Incidentally, after the incandescent lamps with non-directional light, the end for incandescent lamps with reflector technology (so-called spotlights) has now begun. Depending on the type, they disappeared from the market on September 1, 2013 and September 1, 2014. Here, too, as with conventional light bulbs, stocks may be sold off. The halogen spotlights can live a little longer. And incandescent lamps with special properties, e.g. B. with increased impact resistance, may still be produced and offered.

Of course, all other relevant information must be placed on the packaging. With a simple compact fluorescent lamp, this then leads to the pictograms shown below - a total of 18 pieces. Price question (no solution): Who can decipher all pictograms?

LED - the light of the future

Personally, I see compact fluorescent lighting as a transitional technique. In this respect, the ban on incandescent lamps could have simply been postponed until enough suitable LED lamps are available, which is actually the case as early as 2015. Then you could have simply skipped the unfortunate energy-saving lamps. In spite of all energy efficiency, it should of course not be overlooked that lighting is responsible for the largest part of our sensory perception and that the quality of the lighting is therefore also very important. Anyway - let's take a look at new developments ("new" here means 2014/2015).

The development of LED technology is far from over.With the organic LED (OLED) it will be possible in a few years to produce thin, flexible and large-area luminaires and thus even enable luminous ceilings and walls. OLEDs are area light sources, not point light sources. Only a few millimeters thick, they emit their warm and homogeneous light diffusely over the entire surface. They consist of a (glass) substrate, a transparent electrode, one or more organic layers and a counter electrode, which can also be transparent. OLED components are encapsulated and thus protected against oxidation and moisture. They can be dimmed completely and continuously.

Organic molecules usually have a wide emission spectrum. This means that all the color components of the light are present in the spectrum. This enables particularly natural lighting of objects. OLED emissions can be matched to practically any color, including white, of course, with any possible color temperature. Most white OLEDs consist of a red, a green and a blue emission layer, which together produce high-quality white light. A big difference between OLED and LED lies in the parasitic capacitance of the OLED. It has a relatively high self-capacitance, for which many LED drivers are not designed. This can result in high current or voltage peaks when switching on or off or in clocked operation. For this reason, only drivers may be used in which voltage peaks are less than 5% of the nominal voltage and current peaks remain below 15% of the nominal current.

With OLED, there is no exact specification of the service life, because there is a gradual decrease in the luminous flux. The OLED does not burn out in the conventional sense, but loses light output and luminosity over the course of its life. As a rule, the lifetime is defined as the period during which the luminous flux drops to 70% of the original luminous flux (L70).

The development of the LED began in the 1960s. The first red LEDs weren't very bright and efficient yet. It was not until much later that yellow, then green and finally blue LEDs were also developed in the 1990s. With the blue it was now possible to generate white light by mixing the primary colors red, green and blue. At first, the quality of this "white" LED was rather modest, because there were a lot of intermediate colors missing in the color spectrum. Instead of mixing the basic colors, the blue LED light is converted into white light by coating the LED with phosphor. This not only gives you a continuous color spectrum, but also allows you to create different white tones from warm to cold thanks to the type of coating. The coating technology has been continuously optimized since then; at the same time it was possible to get more and more light out of the LEDs. In addition, the light from LEDs is practically free of ultraviolet and infrared light.

White light (like the red, yellow, green and blue tones) cannot be generated directly from the LED chip. It is created either from a mixture of colors, for example from the combination of red, green and blue LED chips (RGB) or from a combination of blue light and a (conversion) phosphor, which is almost always applied to blue LEDs or in the potting compound is integrated that surrounds the chip.

RGB light sources use three monochrome, narrow-band spectra. They can create different color impressions, but are inferior to fluorescent solutions in terms of light quality and efficiency. RGB lighting solutions are therefore more suitable for effect lighting, where the other colors also play a role. The three basic colors are often combined with a white LED (RGBW).

Today, white light for general lighting is mostly generated via wavelength conversion - as was the case with fluorescent lamps, in which the fluorescent substance applied to the inside of the tubes only generates the white light. As already mentioned, a blue LED is combined with a conversion phosphor.

Since LED lamps usually consist of many individual LEDs, a homogeneous white light image can only be created if there are only small color tolerances between the individual chips. This can be achieved by means of "binning", among other things, through appropriate measures in production. "Binning" means the selection of the LED chips according to identical photometric properties (including color location and brightness class). During production, adjusted concentrations of the phosphorus mixtures or different volumes of the potting compound ensure uniform light.

Applying the luminescent layer (source: Tridonic)

In the meantime, the phase of the "LED hedgehogs" and "LED corn cobs" is drawing to a close, LED lamps meanwhile provide a uniform, diffuse and pleasant light. In the meantime there are even LED replacements for fluorescent tubes, which are actually very energy-efficient too. Not only can the classic "light bulbs" be replaced by LED lamps, but also spots and spotlights. This is where LEDs come in with a power that was considered a utopia just a few years ago. With increasing output, however, heat dissipation has also become an important issue for LED lamps. The problem here is the fact that the waste heat is generated on a very small area and therefore has to be dissipated quickly. Only for the halogen pen lamps there is currently no LED replacement. For technical reasons, a corresponding replacement product will not be available in the near future either. Here the switch to LED can only be done by replacing the entire lamp.

Occasionally there are reports of LED lamps that go on and off every few minutes. This is usually due to the fact that the LED lamp has a thermal protection circuit. If it becomes too hot in the lamp, the protective device switches off. The LED cools down and switches on again after a while. Then the whole thing starts all over again. The only solution here is to return the LED lamp to the retailer, the fault is in the product itself.

Incandescent look

Equipping lighting equipment with visible light bulbs was not feasible at all with compact fluorescent lamps and even with many LED lamps from the very beginning. Just imagine the Tivoli in Copenhagen (picture below, press photo Tivoli) with energy-saving lamps.

But this problem has now also found its solution, because the companies Sylvania (Osram) in Germany and Energy World in Switzerland have developed new types of LED light sources with visible filaments, so to speak in the "incandescent lamp look". These new types of LED lamps can hardly be distinguished from conventional light bulbs. At 2700 K, the light color also corresponds to the warm white light of conventional incandescent lamps. Thanks to the new, greatly reduced, linearly arranged LED chips and the glass body filled with noble gas, the large heat sink of other LED lamps is no longer required. The new lamps are available as spheres or candles and other traditional designs are to be added soon. The light output of the new "Sylvania ToLEDo Retro" lamps is quite high at 110 lumens / watt. Therefore, the six-watt version roughly corresponds to a conventional 60-watt light bulb. The service life is also exceptionally long at more than 20,000 hours.

The Swiss manufacturer Energy World refers to its technology as "LCC technology (Laser Crystal Ceramics)." There are tiny wires in the LCC bulb that shine through the ceramic crystal, "explains Daniel Geissmann from XNovum. These are crystals made of a chemically stable and therefore non-toxic gallium-phosphorus compound. The basis of LCC technology is an artificial crystal that replaces the phosphor used in LED technology. Thanks to the artificial crystals, heat is dampened and light The LCC crystals are arranged on the chip in such a way that they bundle the light and enable a higher light output than the LED chip.

Sylvania is more generous with information. The following information comes from an extensive press release. The RetroFit LED (FiLED) lightbulbs have thin threads, so-called filaments, instead of the individual LEDs. Such LED bulbs were first produced by the Japanese company Ushio (www.ushio.com) in 2008. The original USHIO U-LED lamp used six threads to create the appearance of a lightbulb. Each of these filaments contained three LED chips. Other LED chip manufacturers improved the original design. The new LED lamps contain one to four threads on a special carrier strip made of polyester film, which has good electrical and thermal properties.

The LED chips are encapsulated in a transparent column made of glass or synthetic sapphire, stored and coated with phosphor ("chip-on-glass", COG). The column made of glass or synthetic sapphire is only 1.5 mm in diameter but 30 mm long. In the next step, the chips are bonded (connected) with high frequency. This results in an LED strip that can be operated with a higher voltage, which means a lower current and thus lower temperatures. So far this is still a UV LED. The light would not be visible to humans. Then, depending on the desired light color, a phosphor paste is applied and cured. Then the electronic ballast is installed in the base and connected to the connections of the LED strips. Due to the relatively high number of individual LEDs connected in series, the ballasts can remain small. The "filaments" of the FiLED lamps only heat up to 30 to 35 degrees. The glass bulbs are filled with a thermally conductive inert gas (xenon, argon or similar) and welded. The gas causes the necessary heat dissipation to the LED strips. The lamps are not more efficient or inefficient than other LED lamps of the latest generation. The light output corresponds to more than 100 lm / W. You can find out more about this on the Sylvania website.

Sun-like LED light

With the "SunLike" series, Seoul Semiconductor has brought LEDs onto the market, the light of which is almost equivalent to that of sunlight. This natural light spectrum is achieved through the combination of LED chip technology from Seoul Semiconductor and TRI-R technology from Toshiba Materials. Due to their structure, the Sunlike LEDs do not have a dominant blue peak and thus provide light that is better adapted to the human organism.

With conventional LEDs, the generation of white light is based on a blue LED, the light of which is partially converted into yellow and red light by a special phosphor mixture using photoluminescence. The mixture of the blue light of the blue LED and the red and yellow of the phosphor results in white light that contains a more or less high proportion of blue.
(Source: Seoul Semiconductor)
The TRI-R technology for the light conversion of the SunLike LEDs is based on a chip that emits violet light. This light is then converted into the three colors red, green and blue by a phosphor mixture using photoluminescence. Because there is no unconverted light from the LED chip in the spectrum of these LEDs, there is also no undesirable blue peak. The spectrum of this LED light has a more even spectrum.
(Source: Seoul Semiconductor)

The LEDs of the Sunlike series are characterized by very high values ​​for color rendering (CRI) and color quality (Color Quality Scale (CQS)). Since all LEDs with TRI-R technology contain the entire color spectrum similar to sunlight, it is possible, for example, to correctly illuminate gold with all its reflections or a pale skin tone. This opens up applications in architectural and museum lighting as well as in light sources in work, bedroom or hospital rooms.

Spectrum of SunLike LEDs (Source: Seoul Semiconductor)

The SunLike series is produced in four versions with RK-1 in the MJT-CoB housing with 6 W, 10 W, 15 W and 25 W power (as of spring 2018). There is also a 0.2 W version.

Lifespan of LED lamps

The primary argument always brought up in connection with LEDs is their long lifespan. In the initial phase, 100,000 hours were considered, but a value of 50,000 hours or less has now been established for professional applications. However, not all providers mean the same thing. Because various parameters determine the service life of LEDs and this cannot only be determined by the time of their total failure. Most LEDs do not fail at all by the specified point in time, rather the luminosity decreases over time (degradation). The service life of LEDs, modules and lights is therefore limited by two factors:

  • the total failure of the LEDs or the associated electronics or
  • by falling below a previously defined minimum luminous flux
Both essentially depend on the forward current and the junction temperature of the LED. The higher the current through an LED module and the higher its temperature, the faster it ages. In the case of cheap LEDs, there is often another manufacturing reason for the failure: The soldering points are poorly executed and have air pockets. This makes the soldering point hotter during operation and the material expands more. The mechanical stress caused by expansion and contraction when cooling leads sooner or later to breakage of the soldering point and thus to failure of the LED.

If the luminous flux falls below the minimum, one speaks of the rated or useful life of LED luminaires (abbreviation: Lxx). "L70" means e.g. B. a decrease in luminous flux to 70%, whereby the value relates to the entire luminaire and not to a single LED module. The following graph shows the L50, L70, and L80 curves for a specified life of 50,000 hours.

Manufacturers often only give the lifespan in a striking manner and quote high values ​​here. If you take a closer look, you will often find L70 or L80 with brand suppliers, and low-cost suppliers only with L50, who try to achieve a long service life. For example, an LED light with an L70 value of 50,000 hours would have an L50 value of around 85,000 hours. An LED luminaire with an L50 value of 50,000 hours would only achieve an L70 value of around 30,000 hours. Without the specification of the "xx2 in" Lxx "the service life specification is worthless.

Some providers specify the service life information using an additional parameter. In the case of luminous flux degradation, this is the decrease in luminous flux Byy. For example, the specification "L70B50" means a decrease in luminous flux to 70%, with 50% of the luminaires falling below the luminous flux value. A strict value, B10, is often given, i.e. only 10% of the lights fall below the specified luminous flux value. If the B value is missing from a service life specification, B50 automatically applies.

Please do not believe everything you are told. For example, in the broadcast Markt of the WDR on May 16, 2018: "... In the LED there is a crystal with negative and positive electrons ..." We all don't want to hope for that, because then the LED mutates into a fusion reactor in which the two different charged particles radiate into two gamma quanta. Electrons are negatively charged, the positively charged counterpart is called "positron" and occurs very rarely (antimatter) and would immediately disappear through mutual annihilation with electrons.

Switch-on behavior of the various lamp types

Because of their different electrical structure, the inrush currents of the individual lamp types differed quite significantly. By and large, incandescent lamps and halogen lamps behave like resistors. When switched on, the wire resistance is relatively small, but then it increases rapidly as the filament heats up. In the case of incandescent lamps, this results in approximately 10 times the inrush current compared to the rated current at the moment of switch-on. Discharge lamps and many LED lamps have an essentially capacitive switch-on behavior, i. H. they behave in a similar way to a capacitor that is initially discharged and charges very quickly when switched on. With these lamps, what matters is the replacement capacity that the lamp represents. In the case of LED lamps and energy-saving lamps, inrush current pulses in the microsecond range can occur, which are 1000 times the nominal current. If you compare the inrush currents of LED lamps from different manufacturers, they behave very differently with regard to the inrush current, depending on the type of power supply unit used. Presumably, pretty much every technology is represented here, from a switched-mode power supply to a capacitor power supply to a voltage divider.

This is not a problem with the "normal" light switch. The situation is different with switching devices such as B. staircase lighting automats or a normal timer. Depending on the lamp type, the switching device might have to expect inrush currents that differ by a factor of 30 or more. Since the inrush current usually determines the service life of the relay contacts in the switchgear, you should contact the switchgear manufacturer before converting existing lighting (the operating instructions for the switchgear may not be found or they do not yet contain any information on LED lamps). This can prevent problems and failures later.

LED lamps and dimmers

For a long time, LED lamps were not dimmable.Today, the majority is designed for phase-angle dimming and can therefore be operated on most conventional dimmers. And they tend to be more expensive than the normal types too. If the energy-saving or LED lamps are dimmable at all, the dimming curve and the dimming parameters may have to be changed, otherwise the lamps will flicker when dimmed and the following applies: Not every dimmable LED lamp can be dimmed with every dimmer.

When dimming, a triac or thyristor circuit cuts off an (adjustable) part of the rising or falling sinusoidal curve of the mains voltage and thus reduces the active power delivered to the lamp. The darker the lamp appears, the more of the sine wave disappears. With phase control, the dimmer blocks the flow of current to the lamp (incandescent lamp) at the beginning of each sine half-wave. The electronic switch in the dimmer is only switched through after an adjustable time has elapsed. With the next number pass, the current flow is switched off again. This is repeated with every half sine wave. The brightness of the connected lamps can be continuously adjusted by varying the delay time. With phase control, the lamps are switched on when the sine half-wave passes through zero and switched off again after an adjustable time. No interference voltages can arise when switching on because the voltage has the value zero.

Depending on the type of lamp connected, the dimmer must be set to phase control or phase cut. Due to their function, fluorescent lamps and energy-saving lamps can only be dimmed using phase control. Many LED retrofit products work with leading edge and trailing edge dimming. The phasesfromSection dimming leads to little or no noise development (hum). However, while a normal incandescent lamp of 60 W, for example, can be dimmed evenly between 0% and 100%, LED lamps have saddle points in the lower and upper areas (0% ... 20% and 70% ... 100%). There the brightness no longer changes perceptibly. In addition, a higher base load at the dimmer output is necessary for the trailing edge so that it works properly. In addition, each dimmer channel often requires a minimum load of approx. 30 to 50 W. If there is not enough basic load, many LED lamps cannot be switched on or flicker. At the phasesatsectional dimming, the "dimming range" is larger and better dimming behavior is shown. In addition, higher total loads can be connected to a dimmer channel. However, cutting the sine wave results in higher current peaks. These can lead to increased heating of the dimmer and also to high-frequency whirring noises on the lamps.

Because of the current peaks and the resulting warming, you can no longer hang as much load on a dimmer as with a conventional incandescent lamp. As a rule of thumb, experts give a factor of 0.2: If the manufacturer specifies an incandescent lamp load of, for example, 500 W for a dimmer, the maximum load for LED lamps should not exceed 0.2 * 500 = 100 W. In addition to the restricted maximum load, the minimum load also plays a role. With low-power LED lamps, the currents of the interference suppression capacitors built into the dimmers are sometimes sufficient to prevent the LED from going out completely. In such cases, dimming to values ​​below 10 to 20% is no longer possible. Many LED lamps also switch on with a long delay or glow for a long time. The joint operation of conventional and LED lamps on one dimmer output can have further negative effects such as B. cause undesirable current characteristics that result from capacitive and inductive mixed components. Mixed loads are therefore not recommended under any circumstances.

Light and insects

Artificial light attracts insects. In nocturnal animals, artificial light can disrupt their natural rhythm of life. Special insects are attracted to light sources ("Men buzz around me like moths around the light ..."). There are moths that migrate over hundreds of kilometers and presumably orient themselves on the moon and also take into account the relative movement of the moon. But if they mistake a street lamp for the moon, they come closer and closer to the light source on a spiral trajectory. Other insects do not fly on a spiral path around the light source, but directly towards it, only to evade at the last moment and circle the light. A negative example are cockroaches: If you come into a dark room that is inhabited by them and turn on the light, they immediately disappear into any cracks.

But there is a way out: insect eyes are particularly sensitive in the bluish short-wave range. If you compare two typical street lamps, one shines bluish (high pressure mercury vapor lamp), the other emits yellow-orange light (high pressure sodium vapor lamp). Both lamps emit light that is easily visible to humans, but insects are more sensitive to the spectral composition of the light from fluorescent lamps and high-pressure mercury lamps. The light from high-pressure sodium vapor lamps without a UV component, on the other hand, appears darker to them. The proportion of blue light in the white light spectrum is also problematic with LED lighting. In 2014, the New Zealand Scion Institute compared the effects of white LED lamps with yellowish sodium vapor lamps and found that the LEDs attract significantly more insects. But this does not have to be the case, the light from energy-efficient LEDs can also be used in the absence of blue and UV - Proportion of being insect-friendly. In a study of the approach behavior of insects in Frankfurt (Main), six different light sources were equipped with insect trapping vessels and the yield was counted. Warm white LEDs achieved the best results, followed by cold white LEDs.

In 2018, scientists from the Leibniz Institute for Freshwater Ecology and Inland Fisheries in Berlin assume that artificial light contributed to the drastic insect deaths observed for the first time in 2017. The study areas in which the decline was most pronounced were predominantly metropolitan areas. The flying insects would not only, as mentioned above, be attracted to artificial light sources and thus migrate from other ecosystems, but they would also be slowed down in their spread by "light corridors".

Based on these findings, more LEDs with a warm water tint or, even better, those with an orange-yellow color (amber) should be used. Studies and observations from cities like Tucson in Arizona show that modern LED technology can reduce light emissions by two thirds without people perceiving it as darker. In terms of security, it is not even necessary to see colors - clear contrasts are much more important.

Lamp base

As you probably know from your own painful experience, there is an almost unmanageable variety of lamp bases and threads. Probably the oldest thread goes back to Edison and can be found in all "classic" light bulbs. The lamp bases are described by combinations of letters and numbers. The coding provides information about the base or the appropriate socket. The classification is done with one or two capital letters. Lower case letters can also follow for subclasses. The number after the letters gives approximately the value of the dimension (in mm) of the base, e.g. B. diameter or distance of the contacts.
  • B: bayonet socket (longer pins)
  • BA: Bayonet socket for cars (shorter pins)
  • D: sofa lamps
  • E: base with screw thread (Edison thread)
  • F: Socket with individual protruding contact pins or flat plugs Different contact forms are denoted by lower case letters:
    • a: cylindrical pin
    • b: fluted pin
    • c: different pen shape
  • G: Socket with two or more protruding contact pins or flat plugs
  • K: Bi-Post socket with flexible connection
  • P: Prefocus socket (adjustment socket)
  • R: socket with recessed contacts (halogen pin lamps)
  • S: sleeve base
  • Sv: sofa lamp
  • T: base for telephone lamps
  • W: Integrated base as part of the lamp

The following two figures show the most common base shapes for incandescent, energy-saving, halogen and LED lamps.

HV halogen (230 V)  XX     
LV halogen (12 V)    XXX  
Fluorescent lamp T5 L       X 
Fluorescent lamp T8 L        X
Led LampsXX XXXX  

Another interesting information about the standard sockets E14 and E27 ("Edison"): The threads are more or less identical in Europe, but in North America the thread has the same diameter but a different pitch. European lightbulbs can only be screwed into the sockets there with difficulty and vice versa (thanks to H.-J. Grundlach).

More information about lamp bases can be found at:
Lamp table fluorescent lamps (VS)
Lamp base (Osram)

The Osram lighting dictionary offers a lot of interesting information.

Information about the use of LEDs in lighting technology can be found in the ZVEI's guidelines for planning security in LED lighting.

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Copyright © Munich University of Applied Sciences, FK 04, Prof. Jürgen Plate