Black bars on left and right when displaying narrower content on a wider screen.
Definition
Pillarboxing adds black bars to the left and right to display narrower aspect ratios (e.g., 4:3) on wider displays (16:9). The opposite of letterboxing.
Practical Application
Older TV series on modern TVs. Classic film restoration. Stylistic choice for specific scenes. Combined with letterboxing results in "windowboxing."
Technical Details
Pillarbox size = (Screen ratio - Content ratio) / 2. Example: 4:3 on 16:9 = ~12% bars per side. Alternatives: Pan & Scan (loses image information) or Stretch (distorts).