What are the representative symbols and units of luminous flux, light intensity, illuminance and color temperature of LED?

(Light) Intensity: luminous flux emitted by a point light source in a given direction within a unit solid angle, in Candeira (Cd).

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.

The unit of color temperature is k.

The luminous flux is expressed by the symbol φ, and the unit is lumen (lm),1CD =1lm/1Sr (Sr: the unit of solid angular sphericity), the unit of color temperature (k) and the symbol of brightness (l), and the unit is (cd/m? )。

The sum of the energy emitted by the light source and the energy received by the human eye is called luminous flux unit lumen.

Luminous intensity Light comes from different angles with different intensities, so we define the intensity of light emitted by visible light in a certain direction as light intensity, that is to say, the luminous flux unit Candeira cd emitted in a certain direction angle.

Illuminance is the unit lx of the proportional coefficient between luminous flux and illuminated area.

Brightness is the intensity unit cd/M2 of the reflected light of an object seen by the eyes from a certain direction.

Extended data:

When shooting in natural light, because the color temperature of light is different in different time periods, the color of the photos taken is also different. For example, when shooting under a clear blue sky, the color temperature of the light is high, and the photo is cold; But if you shoot at dusk, the color temperature of the light is low, so the photo is warmer. When shooting with artificial light, there are also different types of light sources, and the colors of the photos taken are different.

Understanding the relationship between light and color temperature is helpful for photographers to shoot under different light, calculate in advance what color tone photos they will take, and further consider whether to strengthen or weaken this color tone, and which function of the camera should be used to strengthen or weaken this color tone in actual shooting.

Reference source: Baidu Encyclopedia-Color Temperature