Illumination terminology

Name   Symbol   Unit   Direction

Luminous flux Φ lumen(LM) The amount of luminance which send out from luminary in per second,is light yield.

Luminous intensity   I candela(Cd) Luminous flux which launches in particular direction and the unit solid angle from luminary.
Illumination   E   Lux(Lx) Luminous flux received in per unit areaAverage life   H   hour   The hourage of a bath of light bulbs when 50% are damage and not work.
Economic life H hour  
In simultaneously consider the condition of light bulb’s damage and the output of beam is attenuate,the hourage of synthesis beam output particular proportion.
The proportion used in outdoor,the light source is 70%,when indoor,the light source such as fluorescent light is 80% Color temperature K Color temperature is expressed by absolute temperature K(Kevin),is heats up a standard blackbody(such as iron),when the temperature rises to a certain degree,the color start with red->pale red->orange yellow->white->blue white->blue, changes gradually,using this characteristics of light color change,when the light color of some light source is the same with blackbody presents in a temperature, we called absolute temperature of blackbody at that time as color temperature of its light source.
When color temperature is below 3000K,the light color has phenomenon to began to red,give a warm feeling for human.When color temperature is above 5000K,the color is biased toward to blue,give a chilly feeling for human.
Color rendering index   Ra   
The degree of present which light source to the object color is color rendering index,is also the degree of color lifelike,the light source with high color rendering index is better to appearance of color,the color we see is close to the natural primary color,the light source with low color rendering index is poor to appearance of color,the color deviation we see is also large.
Light source efficiency（Lm/w）=lumen(Lm)/electric power consumption(W)
Glare   In the field of view has objects with brightness extremely high and intense brightness contrast,may cause the visual discomfort,is called glare. Glare divides into incapacitation glare and discomfort glare,it’s the important factor affecting the quality.

Luminous flux
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.