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The difference and relationship between brightness and illuminance

Views: 178 Author: Site Editor Publish Time: 2024-06-26 Origin: Site

The difference and relationship between brightness and illuminance

Brightness and illuminance are two physical quantities that are both related and different.

The unit of brightness is nits or cd/m2, and the unit of illuminance is Lux

Brightness: refers to the brightness of light that a person's eyes perceive when looking at a light source. The brightness level is determined by the color temperature and luminous flux of the light source, and the luminous flux of the light source is the decisive factor. The higher the luminous flux of a light source, the higher the brightness.

Illuminance: refers to the luminous flux per unit illuminated area when a light source illuminates the surrounding space or ground. The higher the luminous flux per unit illuminated area, the higher the illuminance.

The correlation point is that the physical quantity that affects the brightness and illuminance of the light source is common, that is, luminous flux.

Difference 1: The luminous flux that affects the brightness of a light source is the amount of luminous flux emitted from the surface of the light source.

Difference 2: The luminous flux that affects the illuminance of a light source refers to the amount of luminous flux that the light source radiates onto the illuminated surface (such as walls, floors, and work surfaces).

Difference 3: The two are located in different positions and are also affected by different external factors. The luminous flux radiated from the surface of the same light source is not equal in quantity to the luminous flux radiated from the light source to the illuminated surface (such as walls, floors, workbenches).

The brightness and visual perception of a light source are sometimes greatly affected by color temperature. In light sources with the same luminous flux, light sources with high color temperatures will produce an erroneous visual perception of high brightness. This type of "high brightness" light source does not necessarily have higher light efficiency than other light sources, and the illuminance is not necessarily higher than other light sources. It is just a dazzling "false brightness".

In practical lighting application design and energy-saving lighting, the use of spectroradiometers can mainly evaluate the illuminance, especially the effective visual illuminance, and the level of this physical quantity value.

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The difference and relationship between brightness and illuminance

The difference and relationship between brightness and illuminance

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