The differences between luminous flux and Illuminance

Luminous flux is an indicator of the total amount of light emitted by a light source, measured in lumens (lm). It primarily reflects the light-emitting capability of the light source itself - the higher the luminous flux value, the more total light is emitted by the light source, and it is independent of the distance of illumination. It is one of the core parameters of a lighting fixture. 

Illuminance is an indicator of the light intensity received by the illuminated surface, measured in lux (lx), representing the amount of light received per unit area. Under the same light source (with a fixed luminous flux), the closer the illumination distance, the higher the illuminance; conversely, the farther the distance, the lower the illuminance.

The relationship between the two: Under the same irradiation conditions, the higher the luminous flux of the light source, the higher the illuminance on the surface of the illuminated object is usually.