What is Pixel Pitch ?

How to select Pixel Pitch on your application ?
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A) The pixel pitch is the distance between 2 LEDs. The above picture shown the pixel pitch is 4mm, in short, we called it as P4.
B) The smaller pixel pitch, the higher the resolution and better image quality. 
C) Commonly Outdoor Type : P6, P8, P10
                           Indoor Type    : P2, P2.5, P3, P4