Brightness of an LED display is generally expressed by a numerical value in nits, a nit is defined as unit of illuminative brightness described as candela output per square meter. (cd/sqm). The higher the number of nits, the brighter the display.

Brightness is very important to LED display. If the brightness of a LED display is too low, the images shown on the display would be too dark to be seen.
But if the brightness is too high, it will bring a lot problems as follows:
1, Light Pollution.
2,Reduce the LED Display Lifetime. If manufacturer improves brightness through increase module current, tthe modules will be burned easily.
3, More Power Consumption and More Cost.
4, Dazzle Viewer’s Eyes.

For Indoor Fullcolor LED Display, the brightness is enough with 1000cd/sqm to 1600cd/sqm.
For Outdoor Fullcolor LED Display, the brightness is enough with >5000cd/sqm if not face the sun, the brightness is enough with >8000cd/sqm if face the sun directly.