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LED screen brightness and viewing angle.
In different environment condition, the request brightness of LED screen are different according to the environment contrast ratio. 
Indoor LED screen request a lower brightness but high request for viewing angle. Outdoor LED screen's brightness is higher than environmental brightness, and also with better grey degree, therefore its viewing angle request is not as high as indoor one, generally between 35-- 50 degree. 
If the viewing angle of LED lighting part become lower, the brightness will be higher. Vice versa. If the contrast ratio between LED screen's brightness and environmental brightness is higher, the led screen's showing performance will be more colorful. 
Hereby, LED screen's brightness and viewing angle should be fixed by the request of application environment.
 
What is Viewing Angle?
 
In display technology parlance, viewing angle is the maximum angle at which a display can be viewed with acceptable visual performance. In a technical context, this angular range is called viewing cone defined by a multitude of viewing directions.
 
Different Viewing Angles
What is the brightness?
 
The Brightness of an LED screen 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/M2). The higher the number of NITs, the brighter the screen. In general, 1,500 NITs, provides readable text in outdoor daylight, while grayscale and outdoor video require up to 5,000 NITs for acceptable color depth.
The level of the brightness is mainly decided by the quality of the lamp chip.
Common brightness requirements as below:
  1. Indoor: >800CD/M2
  2. Semi-indoor: >2000CD/M2
  3. Outdoor (locate south, face north) >4000CD/M2
  4. Outdoor (locate north, face south) >8000CD/M2
 
What’s the relationship between the viewing angle and the brightness?
 
If the viewing angle of the LED screen becomes lower, the LED screen brightness will be higher, or vice versa. If the contrast ratio between LED screens' brightness and environmental brightness is higher, the led screens' showing performance will be more colorful. However, if the brightness of the LED screen is too high, it is bad for the human eye, and much more power consumption will be wasted. Also much more heat will be produced, and then the temperature becomes much higher. For that the led chip's brightness decreases much faster, and of course, its lifespan will become shorter.
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.
<a title='LED screen' target='_blank'  data-cke-saved-href='http://www.led-star.com' href='http://www.led-star.com' class='seolabel'>LED screen</a> viewing Angle<a title='LED screen' target='_blank'  data-cke-saved-href='http://www.led-star.com' href='http://www.led-star.com' class='seolabel'>LED screen</a> viewing Angle based on 70
 
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 screen 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 screen'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 screen 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 screens from different manufactures. Furthermore, you can differentiate between viewing angle and reading angle. 
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.
 
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