LED 101 / Basics
Viewing distance
How far people sit from the wall decides how fine the pixel pitch needs to be. Rules of thumb help, then the room decides.
Viewing distance is how far the audience is from the face of the LED wall. Sit too close on a coarse pitch and you see the dots. Sit far away on a fine pitch and you paid for detail nobody can use.
A common rule of thumb: take the pixel pitch in millimetres and read it as metres for a minimum comfortable distance. A 3 mm pitch means about 3 metres before the pixels start to blend. Many people then plan a preferred distance around two to three times that number, depending on how critical the picture is. Other rules exist (some use feet instead of metres), so treat any formula as a starting point, not a law.
In a school gym the front row and the back of the bleachers are both real distances. Spec the wall for the closest seats that matter, and check that the far seats still get enough size and brightness. An integrator will walk the room with a laser and a tape before locking pitch.