How does an LED emit light 3

How bright is an LED lamp?

What do units of measurement such as watts or lumens say about the brightness of an LED lamp and how bright are light-emitting diodes in comparison to conventional light sources?

With conventional light bulbs and halogen lamps, the brightness of a light source is directly related to the wattage. Although, strictly speaking, the watt unit does not quantify the brightness, but the output of a light source, the values ​​are clearly indicative. Everyone has exactly one picture in their mind, such as how the brightness of a 40 watt light bulb differs from an 80 watt halogen lamp. Even with modern LEDs, the power of the lamps is given in watts, but it is not that easy to infer the actual brightness of the light-emitting diodes. Much more important for a meaningful assessment of the brightness are other measured variables such as the light output or the luminous flux in lumens or the light intensity in candela.

Luminous flux in lumens and brightness of an LED

The luminous flux is expressed in lumen (lm) and says how much light is emitted from a light source in all directions. Since LEDs consist of different components, all of which have an influence on the brightness of the lamp, the luminous flux or the light output of LEDs is best compared on the basis of their number of lumens. Because even LED lamps with the same wattage can be of different brightness. In connection with the luminous flux in lumens, however, the beam angle of an LED should also be taken into account. This also has a great influence on the actual brightness of the lamp. An LED with 300 lumens and a small beam angle of 20 degrees provides a significantly brighter light in a smaller illuminated area than an LED with 600 lumens but a large beam angle of 90 degrees.

Luminous intensity in candela and brightness of an LED

The light intensity is given in the size candela (cd) and says how much light is emitted by a light source in relation to a certain solid angle. In contrast to the luminous flux in lumens, not all of the light emitted in all directions by an LED is measured here, but only the light emitted exactly on a certain area. In this way, LED lights with different beam angles can theoretically be compared with one another. In practice, however, this procedure is only used extremely rarely. Only very few manufacturers list specific measured values ​​in the data sheets of the LEDs, since they can only be represented as an extremely technical light distribution curve. The background to this is the inaccuracy that arises in the beam angle of an LED due to the decreasing light intensity towards the edge.

Brightness of LEDs compared to conventional light sources

In order to provide an overview of the brightness of LEDs compared to conventional light sources, the values ​​for watts and lumens and their relationship to one another can be used as a guide:
  • A 20 watt light bulb has a luminous flux of around 120 lumens
  • A 40 watt light bulb has a luminous flux of around 420 lumens
  • A 60 watt light bulb has a luminous flux of around 720 lumens
  • An 80 watt light bulb has a luminous flux of around 1000 lumens
  • A 100 watt light bulb has a luminous flux of around 1400 lumens
  • A 20 watt halogen lamp has a luminous flux of around 250 lumens
  • A 40 watt halogen lamp has a luminous flux of around 650 lumens
  • A 60 watt halogen lamp has a luminous flux of around 850 lumens
  • A halogen lamp with 80 watts has a luminous flux of around 1200 lumens
  • A 100 watt halogen lamp has a luminous flux of around 1800 lumens
  • An LED lamp with 2-3 watts has a luminous flux of around 250 lumens
  • An LED lamp with 7-8 watts has a luminous flux of around 450 lumens
  • An LED lamp with 9-10 watts has a luminous flux of around 650 lumens
  • An LED lamp with 11-12 watts has a luminous flux of around 1000 lumens
  • An LED lamp with 19-20 watts has a luminous flux of around 1500 lumens
The following light sources are required to achieve a luminous flux of approx. 100 lumens:
  • 15 watt light bulb
  • Halogen lamp with 10 watts
  • LED lamp with 1-2 watts
The following light sources are required to achieve a luminous flux of approx. 500 lumens:
  • 45 watt light bulb
  • 30 watt halogen lamp
  • LED lamp with 7-8 watts
The following light sources are required to achieve a luminous flux of approx. 1000 lumens:
  • 80 watt light bulb
  • 60 watt halogen lamp
  • LED lamp with 11-12 watts
The following light sources are required to achieve a luminous flux of approx. 1500 lumens:
  • 120 watt light bulb
  • 75 watt halogen lamp
  • LED lamp with 20 watts