In unit time, light source radiated to the surrounded and caused by the energy of the visual,it’s called luminous flux.
Expressed with Φ,the unit is Lumen(Lm)
luminous flux is related to the radiation intensity of light source,and also with the wavelength. Human eyes are most sensitive with yellow and green light of 555mm luminous intensity
Light source of radiation in a particular direction and the unit solid angle,is called the luminous intensity of light source in the direction,and short for luminous intensity.
Expressed with symbol I,unit candela(Cd)　　I＝Φ/W

Φ－all luminous flux with light source of radiation in W solid angles  W－solid angle range of light source(Sr)

Solid angle is angle of a cone,to measure with spherical degree,the unit is steradian( Sr.)　　S=2πr平方(1-COSθ) W=S/r平方=2π(1-COSθ) 

Illumination
Luminous flux received per unit area,called Illumination,expressed with E,the unit is Lx　 E=Φ/S　 Φ－luminous flux(Lm)　 S－exposed area(㎡)
illumination Luminous intensity of luminary in a given direction unit projected area,called illumination,expressed with L.unit is candela per square meter.(Cd/㎡) light of luminary in the θ direction is L＝Iθ/Scosθ
The light of an object is related to the light intensity,and also reflectivity.