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Text on TV Screens

Photograph of a TV screen with subtitlesThere can be problems when text is rendered on low resolution TV screens, and this is particularly important for subtitles, where a viewer may be expected to read these over long periods. There is a well-defined ‘safe area' on a TV screen, well away from the screen boundaries where text is less distorted and graphics do not distort as they can do at the edges. Captions placed at the very edge of some ‘safe areas’ can sometimes be clipped when viewed on a poorly set-up domestic 4:3 receiver / Set Top Box combination, so the safe area is best regarded as the maximum allowable width for captions.

Interlaced TV screens are designed to display moving images, so fine stationary lines can be problematic because they tend to ‘twitter’, as the horizontal elements of a line are rendered differently on each of the two interlaced scans. This can make small patterns or text in graphics difficult to decipher even for fully sighted people. Even though a TV screen may be larger than a computer monitor, the 'safe area', the lower resolution and longer viewing distance mean that the image size on the retina is much smaller than when looking at a computer. This has implications for the interface design and legibility of any typefaces used.

Diagram showing dimensions for one particular safe area

The diagram above shows how one particular ‘safe area’ is defined – designers should take the broadcaster’s advice on which safe area definition to use for their particular application.

The size and position of visual information on the screen may determine whether a blind or partially sighted person can perceive it or not. Text should be displayed sparingly in small paragraphs so it can be read more easily. Light text on a dark background is easier to read on a TV screen. High contrast is always an important factor. A large - 24 point minimum - sans serif typeface should be used. Increased line spacing will increase readability, but this requires more screens to display the same amount of information so clear navigation becomes increasingly important. Multiple columns can be difficult to negotiate.

For digital television services much thought has been given to the display of text and graphics, and a detailed specification can be found in the DTG publication ‘UK Digital TV Receiver Recommendations’.

Examples of these recommendations include:

Useful links can be found on the Ofcom website.

Checklist for text on TV screens

 

 



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