LEDs have a prevalent viewing angle, and they're virtually useless outside of that zone. For example, viewing angle is one of the most confusing terms regarding LEDs. Most people assume that the viewing angle is the angle encompassed by the beam. 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 2ø 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.
Figure 1: LED viewing angle
Figure 2 (below) illustrates how brightness is influenced by a viewing angle of 70°. An LED cluster with a brightness of 8,000 NIT viewed at 50° from off center will be just as bright as a LED cluster with a brightness of 2,000 NIT viewed head on. While a LED is not as bright when viewed at an angle beyond the stated viewing angle, there is still sufficient brightness to illuminate the surroundings, to an extent. Therefore, you can still see with an LED beyond the stated viewing angle. How much further? The answer is dependent on the LED display's brightness, ambient light and contrast conditions. The industry refers to this extended viable usability as the viewing angle. Please note, this is just a general representation and not factual for every LED display with 70° viewing angle. All values are estimates.
Figure 2: Example brightness based on a 70° viewing angle.
Now that you have a better understanding of viewing angle and its relationship with brightness, how does this information help? For one thing, you are now better prepared to compare LEDs from different manufactures.
Just remember this if you go to do it yourself:
• Viewing angle is the angle at which the LED's brightness is halved.