The luminous flux received on a square meter is called illuminance, and the unit is lux (Lx).

Living room, kitchen, about 150 lux (Lx).

Living room, reading, make-up and catering are about 300 lux.

It takes about 600 lux to study, sew and read (long time or small print).

First of all, I want to tell you that light is an electromagnetic wave with a certain wavelength, which gives the human eye a "bright" stimulus. Electromagnetic waves with different wavelengths, although the radiation amount is the same, have different degrees of "bright" stimulation to human eyes, and most wavelengths cannot be stimulated, only 380nm to 780nm can stimulate. Among them, 555nm has the highest efficiency.

Luminous flux, as the name implies, is the amount of light passing through, and the unit is lumen Lm.

Now it is the basic unit in optics. Definition (simplified): When the wavelength is 555nm, the radiation amount is 1 W and the luminous flux is 683 lumens.

Illuminance: luminous flux projected on unit area, in lux.

Brightness: the luminous flux on unit solid angle and unit projection area leaving, reaching or passing through a surface, in nits.