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Basic terms of lighting technology

Today, it is no longer sufficient to judge the light output of a lamp or luminaire only by its wattage. The luminous flux (lumens) and the luminous efficacy (lumens per watt) are much more decisive.

Luminous flux
Unit: Lumen (lm)
Luminous flux refers to the total amount of light emitted by a light source in all directions. It is an important criterion when comparing luminaires.

Example:
A 100 W light bulb produces a luminous flux of approx. 1,000 lumens.

Luminous Efficacy
Unit: Lumens per watt (lm/W)
Luminous efficacy indicates the efficiency of a lamp and is calculated from the ratio of luminous flux emitted to power consumed.

Examples:
Classic light bulb approx. 10 lm/W
Halogen spot approx. 18 lm/W
LED chip approx. 100-170 lm/W

Illuminance
Unit: Lux (lx)
1 Lux = 1 lm/m²
Illuminance refers to the luminous flux incident on a specific surface. It is ultimately the decisive measure for assessing the brightness at a certain point in the room. The further away the light source, the larger the illuminated area and the correspondingly lower the illuminance. The measurement of illuminance in the barn should be done at eye level.

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