Letterboxing 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 videographic image has mattes (black bars) above and below it; these mattes are part of the image (i.e., of each frame of the video signal). LTBX is the identifying abbreviation for films and images so formatted. 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.

Letterboxing is used as an alternative to a full-screen, pan-and-scan transfer of a widescreen film image to videotape or videodisc. In pan-and-scan transfers, the original image is cropped to the narrower aspect ratio of the destination format, usually the 1.33:1 (4:3) ratio of the standard television screen, whereas letterboxing preserves the film's original image composition as seen in the cinema. Letterboxing was developed for use in 4:3 television displays before widescreen television screens were available, but it is also necessary to represent on a 16:9 widescreen display the unaltered original composition of a film with a wider aspect ratio, such as Panavision's 2.35:1 ratio.

Letterboxing can be done when a film transfer is made or as part of an electronic conversion from a widescreen (16:9) to a standard definition (4:3) video signal, and the term letterboxed itself does not imply at which stage (between content origination and presentation) the conversion is done and the mattes are added; a letterboxed picture could have been made so by the film studio that mastered the disc, by the television set that displayed it, or by an electronic device in between.

An alternative to letterboxing is anamorphic widescreen presentation, which squeezes the picture horizontally to fit into a narrower aspect ratio. The player or receiver must correct this distortion by either stretching the image back to its original relative width, for display on widescreen televisions, or letterboxing it (during playback) for display on 4:3 video screens. This image transformation generally requires digital signal processing, so letterboxing was the only way in which films were presented in widescreen on home video prior to the DVD format (with a few exceptions outside the mass market, such as Squeeze LD). Anamorphic widescreen video recordings are sometimes called "anamorphically enhanced", in comparison to letterboxed versions. To represent a film wider than 16:9 (e.g., a 2.35:1 film) on a 16:9 display with no cropping, both anamorphic and letterbox techniques (or letterboxing alone) are required; using the anamorphic technique, the mattes will be smaller but still necessary.

Academy ratio (1.33:1, or 4:3) film or video is sometimes stretched to fill a widescreen (16:9) television display,resulting in distortion in which actors appear shorter and fatter.This horizontal stretching distortion can be avoided by pillar box the image,effected either in the television set or in the video player, e.g. a DVD player.Occasionally, video is shot in a widescreen format and encoded into 4:3 video incorporating letterboxing into the 4:3 image.This effect is common on personal video websites and old documentaries.

If a recording is said to be letterboxed, that implies that the letterboxing was done prior to fixing the recording on the medium. There is a difference between a letterboxed recording (or other source) and a letterboxed picture, as a letterboxed recording will appear letterboxed on every screen – even one that has the same aspect ratio as the source content – while a letterboxed picture may be produced from a non-letterboxed source, in which case it will appear full-screen on a suitably wide display. (The letterboxed source displayed on a wide screen will appear both letterboxed and pillarboxed, so the active picture will occupy a rectangle in the middle of the screen surrounded by mattes on all four sides.) Anamorphic widescreen recordings may mislabeled as letterboxed, which technically they are not.

The term letterbox is sometimes used to emphasize that a widescreen motion picture or video has not been anamorphically encoded for 16:9 screens, thus not taking full advantage of the resolution provided by DVD, high-definition television (HDTV), or other media. Because the black mattes are part of the picture, they take up space in the signal that could be used for active picture information, forcing the picture to use less vertical space in the signal than if it were anamorphically encoded. This results in less vertical resolution in the letterboxed picture than in either an anamorphic or pan-and-scan version (which have the same vertical resolution). The reduced vertical resolution is the main disadvantage of letterboxing.

Early use of the letterbox format

The first use of letterbox appeared with the RCA videodisc (CED) format. Initially, letterboxing was limited to several key sequences of a film (e.g., opening and closing credits), but later it was used for the entire film. The first full letterboxed CED release was Amarcord in 1984, and several others followed. Each disc contained a label noting the use of "RCA's innovative wide-screen mastering technique."

In the cinema and home video

Some cineastes prefer letterbox video formatting of their films. Woody Allen insisted that Manhattan be released letterboxed; Sydney Pollack preferred the widescreen in a bonus segment of The Interpreter DVD, despite there being pan-and-scan and letterbox versions; and Miloš Forman has stated his opinion that the matting distracts the viewer.

In NTSC areas of the world, videocassettes often contained only pan-and-scan versions, but DVD releases tend to be offered in both versions. In PAL areas, which do not suffer so much from low vertical resolution with letterboxed images, letterboxing was more common on videocassettes and is almost ubiquitous on DVDs, with very few films being offered in pan-and-scan releases today.

Movies such as The Graduate and Woodstock that made use of the full width of the movie screen often have the sides cut off and look completely different in non-letterboxed copies from the original theatrical release. This is more apparent in pan-and-scanned movies that remain entirely on the center area of the film image.

On television

Current high-definition television (HDTV) systems use video displays with a wider aspect ratio than standard television sets, making it easier to accurately transfer widescreen films. In addition to films produced for the cinema, some television programming is produced in high definition (and therefore widescreen) and appears letterboxed when presented in the 4:3 aspect ratio for viewing on a standard 4:3 television. Programs broadcast in HDTV are sometimes letterboxed in standard-definition television sets or when shown on an analog broadcast.

In Europe, letterboxing has been the display standard for widescreen cinema on television, because the higher-resolution PAL television system does not degrade letterboxed images as much as the American NTSC system. Together with digital broadcasting that allows 1.78:1 (16:9) widescreen format transmissions without losing resolution, 1.78:1 widescreen television is becoming the European television norm for television materials. Although this is not true of high-definition television, it has the same aspect ratio. Most programming in countries such as Britain and France is in standard-definition letterbox format (adopted in the 1990s); in Germany, most television programming is in the full-screen, 1.33:1 aspect ratio.

On a widescreen television set, a 1.78:1 image fills the screen, however, 2.39:1 aspect ratio films are letterboxed with narrow mattes. Because the 1.85:1 aspect ratio does not match the 1.78:1 (16:9) aspect ratio of widescreen DVDs and high-definition video, slight letterboxing occurs. Usually, such matting of 1.85:1 film is eliminated to match the 1.78:1 aspect ratio in the DVD and HD image transference.

A letterboxed 14:9 compromise ratio is often broadcast in analogue transmissions in European countries making the transition from 4:3 to 16:9, for example on BBC One or ITV1 in the United Kingdom. In addition, recent years have seen an increase of "fake" 2.35:1 letterbox mattes on television to give the impression of a cinema film, often seen in adverts, trailers or television programmes such as Top Gear.

The table below shows which TV lines will contain picture information when letterbox pictures are displayed on either 4:3 or 16:9 screens.

Aspect Ratio on 4:3 screen	525 Line System		625 Line System		.	Aspect Ratio on 16:9 screen	525 Line System		625 Line System		1080 HD Line System
Full Screen (1.33:1)	21-263	284-525	23-310	336-623	.	-	-	-	-	-	-	-
14:9 (1.56:1)	40-245	302-508	44-289	357-602	.	-	-	-	-	-	-	-
16:9 (1.78:1)	52-232	315-495	59-282	372-587	.	Full Screen (1.78:1)	21-263	284-525	23-310	336-623	21-560	584-1123
1.85:1	56-229	320-491	64-270	376-582	.	1.85:1	26-257	289-520	29-304	342-617	31-549	594-1112
2.35:1	73-209	336-472	85-248	398-561	.	2.35:1	50-231	313-495	58-275	371-588	86-494	649-1057

Pillarboxing and windowboxing

Pillarboxing (reversed letterboxing) is the display of an image within a wider image frame by adding lateral mattes (vertical bars at the sides); for example, a 1.33:1 image has lateral mattes when displayed on a 16:9 aspect ratio television screen.

An alternative to pillarboxing is "tilt-and-scan" (reversed pan and scan), horizontally matting the original 1.33:1 television images to the 1.78:1 aspect ratio, which at any given moment crops part of the top and/or bottom of the frame, hence the need for the "tilt" component. A tilt is a camera move in which the camera tilts up or down.

Windowboxing occurs when an image appears centered in a television screen, with blank space on all four sides of the image,, such as when a widescreen image that has been previously letterboxed to fit 1.33:1 is then pillarboxed to fit 16:9. It is also called "matchbox", "gutterbox", and "postage stamp" display. This occurs on the DVD editions of the Star Trek films on a 4:3 television when the included widescreen documentaries show footage from the original television series. It is also seen in The Crocodile Hunter: Collision Course, which displays widescreen pillarboxing with 1.85:1 scenes in a 2.40:1 frame that is subsequently letterboxed. It is common to see windowboxed commercials on HD television networks, because many commercials are shot in 16:9 but distributed to networks in SD, letterboxed to fit 1.33:1.

Many 1980s 8-bit home computers feature gutterboxing display mode, because the TV screens normally used as monitors at that time tended to distort the image near the border of the screen, to such an extent that text displayed in that area became illegible. Moreover, due to the overscanned nature of television video, the precise edges of the visible area of the screen varied from television set to television set, so characters near the expected border of the active screen area might be behind the bezel or off the edge of the screen. The Commodore 64, VIC-20, and Commodore 128 (in 40-column mode) featured coloured gutterboxing of the main text window, while the Atari 8-bit family featured a blue text window with a black border. The original IBM PC CGA display adapter was the same, and the monochrome MDA, the predecessor of the CGA, as well as the later EGA and VGA, also featured gutterboxing; this is also called underscanned video. The Fisher-Price PXL-2000 camcorder of the late 1980s recorded a windowboxed image to partially compensate for low resolution.

Occasionally, an image is deliberately windowboxed for stylistic effect; for example, the documentary-style sequence of the film Rent suggest an older-format camera representing the 4:3 aspect ratio, and the opening sequence of the Oliver Stone film JFK features pillar boxing to represent the 1960s era 4:3 television footage. The film Sneakers uses a windowsboxing effect in a scene for dramatic effect.

See also

• Active Format Description
• List of film formats
• Motion picture terminology

References

1. Amarcord CED Web Page
2. BBC Technical Standards for Network Television Delivery 2008, bbc.co.uk, page 8.
3. " Televisual letterboxes", Image Dissectors.com, URL accessed October 4, 2009
4. A visual reference to common Pixel Aspect formats
5. Home Theater: Audio & Video Glossary - ACME HOW TO.com
6. HDTV

External links

• The Widescreen and Letterbox Advocacy Page
• Why Widescreen?
• Widescreen Resources & Information