Luminous flux
The light emitted by a light source per unit time is called the luminous flux of the light source φ Represent, unit name: lm (lumens).
light intensity
The luminous flux emitted by the light source in the unit solid angle of a given direction is defined as the light intensity of the light source in that direction, expressed as I.
I=Luminous flux at a specific angle Ф ÷ Specific angle Ω (cd/㎡)
brightness
The luminous flux per unit area per unit solid angle of the illuminant in a specific direction. Represented by L. L=I/S (cd/m2), candela/m2, also known as grayscale.
illumination
The luminous flux received per unit area, expressed in E. Lux (Lx)
E=d Ф/ dS(Lm/m2)
E=I/R2 (R=distance from the light source to the illuminated plane)