1. Differences in Brightness Units
Lumen (Lumen): Measures the total luminous flux emitted by a light source, i.e., the amount of light perceived by the human eye. It is typically used to describe the overall brightness of light bulbs or fixtures.
Lux (Lux): Measures the intensity of light per unit area, i.e., the brightness when 1 lumen of luminous flux is evenly distributed over 1 square meter. It is commonly used in lighting design (e.g., room illumination).
Nit (Nit): Measures the surface brightness of a light source, i.e., the luminous intensity per square meter (candela per square meter, cd/m²). It is specifically used to describe the brightness of light-emitting surfaces such as displays and LED signs.
2. Why Are Nits (Nit) Used for LED Signs?
The core function of an LED sign is to display information through light emission, and its brightness depends on the intensity of the light-emitting surface rather than the total luminous flux or ambient illumination. Nits (Nit), as a unit of surface brightness, are more suitable for describing the performance of LED signs for the following reasons:
Directly Reflects Visibility: The higher the nit value, the better the visibility of the sign in bright environments (e.g., sunlight).
Industry Standard: Display and LED sign manufacturers commonly use nits as the brightness standard, facilitating cross-comparisons.
Precise Measurement: Nits directly measure the brightness of the light-emitting surface, whereas lumens and lux are better suited for describing the overall output of a light source or ambient illumination.
3. Examples
LED Sign: If an LED sign has a brightness of 10,000 nits, it means the brightness of its light-emitting surface is 10,000 cd/m². This high brightness ensures clear visibility even in direct sunlight.
Light Bulb: An 800-lumen bulb may illuminate a room, but its brightness cannot be directly measured in nits because it is not a light-emitting surface.
Ambient Illumination: The standard illuminance for an office is about 500 lux, which is the intensity of light falling on a surface, not the brightness of the light source itself.
4. How to Choose the Right Brightness Unit?
Overall Brightness of a Light Source: Use lumens (e.g., light bulbs, fixtures).
Ambient Illumination: Use lux (e.g., room, street lighting).
Brightness of a Light-Emitting Surface: Use nits (e.g., LED signs, displays).
