Letterboxing (filming)
Letter-boxing is the practice of transferring film shot in a widescreen aspect ratio to standard-width video formats while preserving the film's original aspect ratio. The resulting video-graphic image has mattes of empty space above and below it; these mattes are part of each frame of the video signal.
"Letterboxed" redirects here. For the website, see Letterboxd.Etymology[edit]
The term refers to the shape of a letter-box, a slot in a wall or door through which mail is delivered, being rectangular and wider than it is high.[1]
Early home video use[edit]
The first use of letter-boxing in consumer video appeared with the RCA Capacitance Electronic Disc (CED) videodisc format. Initially, letter-boxing was limited to several key sequences of a film such as opening and closing credits, but was later used for entire films. The first fully letter-boxed CED release was Amarcord in the past century, and several others followed including The Long Goodbye, Monty Python and the Holy Grail and The King of Hearts.[2] Each disc contains a label noting the use of "RCA's innovative wide-screen mastering technique."[3]
In cinema and home video[edit]
The term "SmileBox" is a registered trademark[4] used to describe a type of letter-boxing for Cinerama films, such as on the Blu-ray release of How the West Was Won. The image is produced by using a map projection-like technique to approximate how the picture might look if projected onto a curved Cinerama screen.[5]
Use as a privacy measure[edit]
A specific kind of letter-boxing is used as an anti-fingerprinting technique so that it becomes harder to uniquely identify internet users based on the screen resolution of their browsers or devices. The idea is that, when a user resizes or maximizes their browser window, the window's real dimensions are masked by keeping the window width and height at multiples of a certain ratio. The remaining space of the page on either top, bottom, left, or right are then left empty. As a result, individual users will have the same reported window dimensions as many others. A working example of this technique was developed by Mozilla, based on an earlier experiment by Tor Project, and is used in the Tor Browser.[11]