Letter Box (レタボ／レターボックス - Letter Box: Video aspect ratio display format, black bars, and comparisons with Pillar Box and Squeeze)

"Retabo" (レタボ) is a widely used Japanese television and media shorthand for "Letter Box" (レターボックス), referring to a video display format that places black bars on the top and bottom of the screen to project widescreen footage without distortion.
It is primarily utilized when displaying ultra-wide cinematic scales (such as CinemaScope) on standard 16:9 widescreen television panels while perfectly preserving the original filming proportions.

Why is a Letter Box Format Necessary?

Widescreen cinematic content like CinemaScope features aspect ratios much wider than standard 16:9 television screens. If displayed directly on a 16:9 panel, the left and right edges of the film would be cut off.
To prevent this cropping, the video is scaled down so the entire width fits the screen, and black horizontal bars are added to the top and bottom to fill the remaining screen space. This is the primary function of a letter box.
The name "Letter Box" originates from the visual similarity of the framed screen to the slot of a traditional mail delivery mailbox (letter box).

Practical Usage Examples

• "This movie is scheduled to be broadcast in a retabo (letter box) format."
  Noting that a film will air on television with horizontal black bars on the top and bottom of the screen.
• "While modern screens are widescreen, classic films are often displayed in a retabo format."
  Discussing how old movies shot in aspect ratios wider than 16:9 are routinely broadcast or streamed in letterboxed configurations.
• "This raw footage has been retabo-processed."
  Referring to the video editing process of adding horizontal black masking bars to a video project.
• "Remember this is a retabo edit, so keep the subtitles clear of the black bars."
  A video production warning advising staff to ensure text and lower-third graphics do not overlap the top or bottom black mask boundaries.
• "This program is broadcasting archival 4:3 SD content in a retabo format."
  Referring to a broadcast state where legacy 4:3 video is shown on a 16:9 stream by adding framing bands.

Related Aspect Ratio Formats

Aside from Letter Box, several other technical formats exist to adjust varying video aspect ratios to fit display panels:

• Pillar Box / Side Panel (ピラーボックス):
  The reverse of a letter box. It places vertical black bars or custom graphics on the left and right sides of the screen to display legacy 4:3 footage on modern 16:9 displays. Also colloquially referred to as "picture framing."
• Squeeze (スクイーズ):
  A format that horizontally compresses a 16:9 video stream to fit entirely inside a classic 4:3 frame, making objects look tall and thin unless unstretched by the display.
• Crop (クロップ):
  A method that crops the top, bottom, or sides of a video frame to force it to fill the entire display area.
• Zoom (ズーム):
  Symmetrically expanding the entire video frame to fill the display panel, resulting in cropped borders.

Pros and Cons of Letterboxing

Advantages

• Preserves the exact artistic aspect ratio intended by the director.
• Allows viewers to see the entire frame without any visual cropping or data loss.

Disadvantages

• Since it does not utilize the full screen area, the active video size appears smaller.
• Some viewers may find the presence of black bars distracting.