Glossary

Pixel density (PPI)

Pixels per inch — how many physical pixels fit in one inch of display. Higher PPI means finer detail and less visible pixel structure at a given viewing distance.

PPI is derived from screen resolution and physical size. A 6.1" 1170×2532 phone yields ~460 PPI; a 27" 4K monitor yields ~163 PPI; a 27" 1440p monitor yields ~109 PPI.

Perception thresholds

At typical viewing distances:

Phone (30 cm) — 400+ PPI is "retina"; eye cannot resolve individual pixels.
Laptop (50 cm) — 200+ PPI is retina.
Desktop monitor (70 cm) — 140+ PPI is retina.
Living-room TV (3 m) — 4K at 65" (68 PPI) exceeds retina; 8K returns no perceptual gain at normal distances.

Why it matters

Below the retina threshold for your distance, text aliasing and pixel grid become visible. Above it, additional PPI is wasted on performance cost without perceived benefit.

Where this matters