What is Digital Widescreen TV?

'Widescreen' is the term used to describe the picture format of digital television broadcasts. The ratio 16 x 9 (sixteen by nine) refers to the ratio of picture width to picture height. Widescreen TV provides a more natural match for the human field of view.

Viewing a 16 x 9 image on a 4 x 3 screen

16 by 9 aspect ratio photo showing a man standing on a mountain top with the sun and clouds behind him

Original 16 by 9 picture

 Central 4 by 3 portion of the same 16 by 9 aspect ratio photo showing a man standing on a mountain top with the sun and clouds behind him

Centre cutout

 Letterbox view, with black bars above and below, of the 16 by 9 aspect ratio picture.

Letterbox

The set top boxes have a set-up menu which allows the viewer to tell the box the shape of the TV screen being used to display digital programmes. You can then tell the box how you would like to view a 16 x 9 image - either letterbox or centre cutout.

The remote handset will then allow you to switch between the default setting and the other depending on how you want to view a particular programme. Additionally the broadcasters are transmitting signals to tell the set top box (or integrated TV) what format of programme is being broadcast.

What information is lost if I fill my screen with centre cutout view of a 16 x 9 programme?

The broadcasters are framing the action within a 4 x 3 active picture area, so you only lose the extra peripheral information that fills the far left and right of the 16 x 9 scene.

Sport is a good example of this - some rugby matches are shot and broadcast in 16 x 9, the widescreen viewer sees the main action with lots of extra information such as other players near the featured scrum. The 4 x 3 analogue viewer or the digital viewer using centre cut out sees the main action - the scrum - as normal.

Viewing a 4 x 3 image on a 16 x 9 screen

Conversely, a widescreen set has to know how you want to display a 4 x 3 image - zoomed or pillarbox and will revert to a full width display when told that a 16 x 9 image is being sent. Manufacturers call zoomed by a variety of names - Panorama, Cinema, Zoom, Stretch and so on.

Original 4 by 3 aspect ratio photo showing a man standing on a mountain top with the sun and clouds behind him.

Original 4 by 3 picture

With a zoomed picture, the intention is to expand the original 4 x 3 picture area to fill a widescreen display.

Picture zoomed in but loosing some of the top and bottom of the image.

Zoomed

Unfortunately either some of the image is lost at the top and bottom of the screen ...

Picture streteched horizontally to fill the screen.

Stretched

... or some distortion is introduced as the width is stretched to fill the screen without changing the height.

The 4 by 3 image is shown normally on the 16 by 9 display and there are black bars to either side to fill the horizontal space.

'Pillar Box'

Finally the 'pillar box' option has black boxes on each side.

It's important to get the right combination of display format and the format of the transmitted programme otherwise you end up with tall thin or short fat images in place of the correctly balanced picture!