14:9 is a compromise aspect ratio of 1.56:1. It is used to create an acceptable picture on both 4:3 and 16:9 televisions, conceived following audience tests conducted by the BBC. It has been used by most UK, Irish, French, Spanish and Australian terrestrial analogue networks, and in the United States on Discovery Networks' HD simulcast channels with programming and advertising originally compiled in 4:3. Note that 14:9 is not a shooting format; 14:9 material is almost always derived from either a 16:9 or 4:3 shot.
With native 16:9 material
A common usage is for material shot in 16:9 format. During production, the important action is kept within the centre of the picture, known as the 14:9 safe area. When the material is broadcast in a 4:3 format (such as for analog television), the sides of the image are cropped to 14:9 and narrow black bars are added to the top and bottom. It is considered that viewers who are not used to wide-screen will find this less distracting than the letterbox format that would result from broadcasting the full 16:9 picture in analogue, while still seeing more of the picture than would be visible if cropped into 4:3. When the same material is broadcast in 16:9 (such as for digital television) the full 16:9 frame is left intact, but auxiliary signals tell the receiver that the picture is suitable for cropping to 14:9 if necessary (for example, when the receiver is connected to a 4:3 display).
The major benefit in shooting 16:9 with protection for 14:9 (rather than 4:3) is improving the usable screen real-estate for titles, logos and scrolling text. The visible enhancement is significant due to the restrictive requirements of overscan. When shooting in 16:9 for potential 4:3 distribution the "Shoot And Protect" method (from the BBC's "Widescreen Book") is employed. As the name suggests footage is shot in 16:9 but important visual information is protected inside the 14:9 or 4:3 safe areas.
With native 4:3 material
Another use is for material shot on a 4:3 format. When broadcast in 16:9, the top and bottom of the original frame are cropped to 14:9, and black bars (called pillarboxes) are added to either side. When broadcast in 4:3, the 14:9 crop is often used in preference to the original 4:3 frame. This is especially common when 4:3 footage needs to be included in an otherwise 16:9 program, such as a news broadcast, and was used in the 2000s by the BBC's children's channels (CBBC & CBeebies) to broadcast older children's programming shot in 4:3 (e.g. ageing schools programming) on a larger proportion of a 16:9 screen. In the case of the BBC's children's channels, additional graphics are added to the pillarbox area instead of leaving it black.
Adoption by TV channels
In the UK, most channels broadcast in 16:9, but some channels such as Nickelodeon also use 14:9. On these channels, the 14:9 cropping is used on adverts and shows which were produced in 16:9, such as House of Anubis, iCarly, Victorious and Big Time Rush, to present a more consistent output. Nickelodeon (UK & Ireland), along with its sister channels Nick Jr. (UK & Ireland) and Nicktoons (UK & Ireland), were the only children's channels that were not shown in 16:9, but made the switch in 2013. The HD channel, Nickelodeon HD was already shown in 16:9 before this, with 4:3 programming shown in the pillarbox effect.
The public broadcaster RTP used the 14:9 format to convert 16:9 broadcasts to the 4:3 format it still uses. However, since June 8, 2012, they began to broadcast 16:9 material in its original aspect ratio, with the correct flag, thus ending the broadcasts featuring the 14:9 format. Private broadcaster TVI started using the 14:9 format in August 2012 to broadcast 16:9 material instead of using 4:3 Pan & Scan, as they refuse to broadcast in 16:9.
VIACOM uses the 14:9 format to convert 4:3 programming to 16:9.
The aspect ratio of 14:9 (1.555...) is the arithmetic mean (average) of 16:9 and 4:3 (12:9), . More practically, it is approximately the geometric mean (the precise geometric mean is ), and in this sense is mathematically a compromise between these two aspect ratios: two equal area pictures (at 16:9 and 4:3) will intersect in a box with aspect ratio the geometric mean, as demonstrated in the image at top (14:9 is just slightly wider than the intersection). In this way 14:9 balances the needs of both 16:9 and 4:3, cropping or distorting both about equally; similar considerations were used in the choice of 16:9 by the SMPTE, there balancing 2.35 and 4:3.