Viewing Angle + Brightness

Viewing angle is one of the most confusing terms regarding electronic LED signs. Most people and manufacturers assume that the viewing angle is the angle at which you can view an electronic display. In reality, viewing angle is related to brightness. The LED industry defines viewing angle as the full angle at which brightness is half of the brightness from dead center. More scientifically, if ø (angle theta) is the angle from off center (0°) where the LED's brightness is half, then is defined as the full viewing angle, as represented by Figure 1 below. The entire yellow portion represents a 70° viewing angle, while the orange portion represents a 90° viewing angle.

Illustration of LED sign's viewing angle.
Figure 1: LED Sign Viewing Angle.

Brightness in relation to LED display's viewing angle.
Figure 2: Example brightness based on a 70° viewing angle.

Figure 2 illustrates how brightness is influenced by a viewing angle of 70°. An electronic messaging display with a brightness of 8,000 NIT viewed at 50° from off center will be just as bright as a LED display with a brightness of 2,000 NIT viewed head on. While a LED display is not as bright when viewed at an angle beyond the stated viewing angle, there is still sufficient brightness to read the display. Therefore, a viewer can still read a LED display beyond the stated viewing angle. How much further? The answer is dependent on the LED display's brightness, ambient light and contrast conditions. We refer to this extended readability as the reading angle. Please note, this is just a general representation and not factual for every LED display with 70° viewing angle. All values are estimates.

Now that you have a better understanding of viewing angle and its relationship with brightness, how will this information help you? For one thing, you are now better prepared to compare LED displays from different manufactures. Furthermore, you can differentiate between viewing angle and reading angle. Lastly, Grandwell always follows the industry standard for specifying viewing angles and will not embellish it like some other manufacturers.

In summary and as reference:
• Viewing angle is the angle at which the LED's brightness is halved.
• Reading angle is the angle at which a typical person can adequately read an electronic message center.
• The reading angle is typically more than the viewing angle.

ISA, International Sign Association