With so many different types of measurements and contributing factors to overall LED sign brightness, the topic can quickly become confusing. However, the sign industry has settled on a standard measurement that will help you to discuss and compare LED signs: the nit. Also known as “candelas per square meter”, a nit is a unit of measurement for the total brightness over one square meter of an LED display. This value takes into account all of the contributing factors to brightness, such as the number of LEDs per pixel, the pixel pitch (distance between pixels) and the brightness of individual LEDs.
This measurement is different than what is typically used for single light sources such as projectors and flashlights, which are measured in lumens. As the light source gets farther away from the surface it is projecting on, the brightness per square meter decreases (think of this as the same amount of light spread over a larger area).
This measurement assumes that all of the LEDs within the square meter are on at their full brightness as allowed by the sign software and hardware configuration. This means the sign is at its brightest white for a full color display, or brightest red for a shaded red display. A special measurement device is used to deliver the nit rating of the sign. Outdoor LED signs can range from 5,000 to 8,000 nits or higher. In comparison, typical televisions range from 500 to 1,000 nits and indoor LED signs from 1,000 to 2,000 nits.
Why does brightness matter?
There are two important things to consider related to sign brightness: how well it competes with the sun, and how long it will compete with the sun. Ensuring that your sign is readable during the day is vital to the success of having passers by read your sign. The brighter the display, the better able it is to compete with the sun.
In addition, LEDs do not burn out but instead grow dimmer with use. The dimmer an individual LED becomes, the less effective the overall sign is at competing with the sun. Starting with a brighter display ensures that your LED sign will be readable for many years into the future.