Technical terms in the lighting industry

Issuing time:2018-12-17 00:00

The technical terms in the lighting industry include luminous flux, illuminance, luminous intensity, brightness, color temperature, color rendering index, luminous efficiency and power factor.


Luminous flux

Luminous flux is the energy that the light source radiates to the surrounding space per unit time and causes vision , represented by the symbol φ, and the unit is lumens (lm).


Illuminance is used to show the light intensity on the illuminated surface (point). The ratio of the luminous flux projected on the illuminated surface to the area of the illuminated surface is called the illuminance of the surface, represented by the symbol E. The unit of illuminance is lux.

Luminous intensity

The spatial scale of the luminous flux radiated within a unit solid angle (per steradian) of the light source in a specific direction in space is the luminous intensity of the light source in that direction (abbreviated as Luminous intensity), represented by the symbol Iθ, and the unit is candela (cd).


The light intensity of the illumiants unit projection surface from the gazing direction is called the objects surface luminous intensity , represented by the symbol L, and the unit is nit (nit).

Color temperature

When the color of the light emitted by the light source is the same as the color radiated by the "black body" at a certain temperature, the temperature of the "black body" becomes the color temperature of the light source,the unit is lumens (K).

Color rendering index

The degree to which the light source presents the color of the object is the color rendering index, usually called "Color rendering index" (Ra).

Luminous efficiency

Luminous efficiency of an electric light source is expressed in terms of how many lumens produced by consuming 1W of electric power, which is the ratio of luminous flux to power, and the unit is flow/watt (lm/W). The higher the luminous efficiency, the better.

Power factor

Power factor is the power grid, commonly known as power grid waste. The higher the power factor, the less impact and the better the effect. It is the ratio of useful power to apparent power (the product of voltage and current) in the circuit, represented by the symbol PF.

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