As a signage professional, it is worth your time to know about an important feature of LED illumination. That is the “viewing angle”, and the meaning of that angle is sometimes misinterpreted.
Here is a capsule explanation. The textbook definition of a viewing angle is “the peak luminous intensity measured at right angles to the surface of the LED chip”.1 It is twice the number of degrees from vertical at which luminous intensity drops to half of the peak value.
In other words, the viewing angle tells you the space covered by the “cone of light” prior to losing half of its peak illumination level. It is simply a measure of the position where the intensity of the LED light spread reaches 50% of its maximum brightness.
One common misconception is the illumination completely dissipates at the edges of the viewing angle. It doesn’t – LED modules do not produce a “flashlight beam”. The illumination continues past the edge of the viewing angle but continues to decrease in intensity. 1. http://www.arrownac.com/solutions-applications/lighting/whatisanled.html