Note 001 · S1 Parameters · 20 Oct 2026
Pixel pitch, viewing distance and the one-metre rule — and where the maths breaks
The rule is one metre of viewing distance per millimetre of pitch, and it holds for most rooms. It fails for text content, for sun-facing walls, and for any project where the audience never stands where the drawing says they will.
Allow 1 metre of viewing distance per 1 mm of pixel pitch: P1.5 holds from 1.5 m, P2.5 from 2.5 m, P4 from 4 m. In a lobby whose nearest viewer stands 3 m away, P2.5 is the coarsest pitch that still holds and P4 shows its grid. Decide it from where people actually stand.
Why the rule exists at all
A pixel grid becomes visible when its individual pixels subtend a large enough angle on the eye. For a normal-sighted viewer the threshold sits close to one arc-minute per pixel, and at every distance people actually use, that works out to roughly one millimetre of pitch per metre of distance. It is a rule of thumb, but it is a rule of thumb with a physical basis rather than a marketing one.
Two things follow. The first is that pitch is not a quality grade — it is a distance requirement. A P4 wall at six metres is not worse than a P1.5 wall; it is a different answer to a different sightline. The second is that the spec sheet cannot tell you which one you need, because the spec sheet does not know where your audience stands.
The working table
| Pitch | Minimum distance | Where it fits |
|---|---|---|
| P1.5 | 1.5 m | Control room desk, close retail counter, boardroom table |
| P1.9 | 1.9 m | Meeting room, studio backdrop, reception desk |
| P2.5 | 2.5 m | Lobby, showroom, most retail sightlines |
| P4 | 4.0 m | Atrium, large hall, stage edge |
| P6.67 | 6.7 m | Façade seen from the far side of a road |
Distances are the nearest standing position, not the room's diagonal.
How to apply it on a real drawing
Take the plan, mark the places a person can physically stand, and find the closest one. That distance, not the room's diagonal and not the client's wish, sets the pitch. Then check the two cases below, because they move the answer by a step in opposite directions.
If the nearest viewer stands under 2 m, then go P1.9 or finer. If they stand 2.5–4 m away, then P2.5 holds and P4 shows its grid. Beyond 4 m, P4 costs less and shows no difference.
Where the rule stops holding
1. The content is text, not video. Letters have edges thinner than a pixel, so the comfortable distance roughly doubles. A P2.5 wall that reads well as video at 2.5 m needs about 5 m before body text stops shimmering — or a finer pitch.
2. The wall faces the sun. The limit stops being pitch and becomes contrast between lit pixels and ambient light on the glass. In that case pitch matters less than you expect and reflectivity matters more.
3. The audience is not where the drawing says. Queues form at the till, not at the plan's viewing point. If the real nearest viewer is 1.2 m away, a P2.5 wall is the wrong answer no matter what the table says.
One thing we got wrong ourselves
We used to quote this rule against the room's far wall, on the argument that the buyer would judge the image from the back of the room. That is backwards: a wall is judged from wherever people walk past it, which is usually the closest point, not the furthest. We changed the method in 2023 and quote against the nearest standing position now.
- Practice — Sightline checks on installed walls in retail and lobby settings, from our own projects. This is field experience, not a recorded measurement series.
- Datasheet — Panel pixel pitch and module dimensions, from the manufacturer's current sheet for each series.
- Practice — The one-arc-minute threshold and the one-metre rule as commonly used in the industry. It is a convention, not a standard, and no test certificate exists for it.
Questions we get on this
No. Pitch is a distance requirement, not a grade. At 4 m of nearest viewing distance a P2.5 wall is the correct answer and a P1.5 wall costs more for no visible gain.
No. Text roughly doubles the required distance, because letter edges are thinner than one pixel. A P2.5 wall that looks clean as video at 2.5 m needs about 5 m for body text.
If your sightline is unusual, this table will not be enough.
Send the plan with the nearest standing position marked and we will answer with a pitch and the distance it holds to — in writing, with the exception stated.