Relationship between light intensity and lumen in IES

Light intensity = illuminance (luminosity) x square of distance, which is true when the light source is a point light source!

The definition of luminous intensity takes into account human visual factors and optical characteristics, and is based on human vision. Confusingly, in optics, light intensity often refers to the radiation power per unit area. Because the relative visibility of light with different wavelengths is different, when the radiation power of light with different wavelengths is equal, its luminous flux is not equal.

Luminous flux unit. The total amount of light emitted by a luminous flux light source is expressed by f ... and its unit is lumen (Lm). For a point light source with luminous intensity of 1 candle, the luminous flux per solid angle (1 sphericity) is "1 lumen". Lumen is Lumen.

The relationship between lightness and illuminance is that illuminance is equal to lightness per unit area.

Conversion method: luminosity divided by area equals illuminance. Luminance is the main technical index of projector, which is usually expressed by luminous flux, while illuminance is a physical term, which refers to the luminous flux of visible light received per unit area. Luminous flux is the ability to describe the intensity of visual response produced by light source radiation in unit time, and the unit is luminosity.