Pillar box

The pillar box effect occurs in widescreen video displays when black bars (mattes or masking) are placed on the sides of the image.

It becomes necessary when film or video that was not originally designed for widescreen is shown on a widescreen display, or a narrower widescreen image is displayed within a wider aspect ratio, such as a 1.85:1 image in a 2.35:1 frame. The original material is shrunk and placed in the middle of the widescreen frame. Some older arcade games that had a tall vertical and short horizontal are displayed in pillarbox even on 4:3 televisions.

Pillar boxing is the vertical equivalent of letterboxing and is sometimes called reverse letterboxing. Its name is derived from its resemblance to pillar box-style mailboxes used in the UK and the Commonwealth of Nations. The four-direction equivalent is called windowboxing. Likewise, the vertical equivalent of pan and scan is called "tilt and scan" or "reverse pan and scan."