Luminous flux

What ist luminous flux?

Luminous flux is a photometric quantity and describes the total amount of visible light emitted by a light source. It takes into account the fact that the human eye perceives light of different wavelengths with varying degrees of sensitivity. The symbol for luminous flux is Φᵥ, and its unit of measurement is lumen (lm).

However, luminous flux does not provide any information about how the light is distributed spatially. Two spotlights with the same luminous flux can therefore produce different light patterns and illuminate a working area to varying degrees.

With LED spotlights, a distinction is also made between theoretical and actual luminous flux. The articles Lumen and Effective Lumen explain this in more detail.

Basic information on the measurement and evaluation of visible light is provided in the article Photometry.