LED 101
This is a great article published in Live Design and written by Fabio Aversa.
It outlines the fundamentals of modern LED display technology including the concept of the pixel and the basics of display construction.
IP - Ingress Protection rating
When shopping for an LED display, you will hear a lot of terminology that you may or may not be familiar with. One of these is the LED display’s cabinet environmental "IP" rating. This reference table gives the definition of the IP rating system. Most LED screen designed for outdoor use are IP65, meaning it offers complete protection from dust intrusion and low pressure water jets from all directions (hose down) Depending on the LED screen vendor and the intended usage of the display, some displays are IP65 from the front (the LED side) and IP53 from the rear. IP53 promises Dust protection and Spray water (any direction up to 60° degrees from the vertical Heavy Rain). You should be cautious and test the design yourself to see if a cabinet rated IP53 will indeed provide all the protection you will require depending on the display’s final installation location. Some form of external weatherproofing may be required.
Dot Pitch and Pixel Pitch
The distance between pixels on a display is called Pitch
This is the physical measurment between pixels
The technique used to determine pitch is to measure from one LED of one color, to the next LED of that color.
Example: Blue LED of pixel #1 to Blue LEd of Pixel #2)
Shared Pixel vs Virtual Pixel
Many vendors have tha ability to use techniques to increase the video resolution of their displays.
These techniques are very frequently confused for each other.
Virtual Pixel
To virtual pixel display typically consists of a square pixel with 2 Red LEDs, 1 Green LED and 1 Blue LED.
The value of each of these diodes is collected from 4 pixels in the video source.
Pixel Sharing
To display using pixel sharing actually uses LEDs from adjacent pixels to create new pixels.
Both techniques are used to double the captured area of the video signal.
A display 128px x 128px will capture a 256px x 256px area of video.
Sometimes, these features are used to sway unsuspecting buyers into believing they are buying a higher resolution display than they actually are.