The typeface Tiresias Screenfont was originally designed for subtitling on UK digital television in 1998 by a team led by Dr John Gill. It has been specifically designed for screen display and has been adopted by the UK Digital Television Group as the resident font for interactive television. Screenfont is now being adopted for European digital television. Its use is also being considered in the USA.

Tiresias Screenfont has been designed to have characters that are easy to distinguish from each other. The design was carried out, with specific reference to persons with visual impairments, on the philosophy that good design for visually impaired persons is good design for everybody.

The design process

Throughout the design process, the key factors that affect legibility were studied.

These included:

• Character shapes.
• Relative weight or thickness of the character shapes.
• Inter-character spacing.
• Aspect ratios that affect the maximum size at which the type could be used.

Tiresias Screenfont has been designed with a medium weight. Special consideration has been given to character shapes that could be difficult to distinguish. For people with low vision some numerals such as 6, 8, and 9 can be confused. Tiresias Screenfont has open shapes, designed to make each character as clear as possible.

Characters such as the lower case 'l' have been designed to ensure they are different from the numeral '1' or a lower case 'i'. The tail on the 'l' also helps stop two 'l's merging. These factors may not seem important to persons with good vision but to a person with low vision they can make all the difference. Further information is given in a Design Report (LINK).

Testing

Tiresias Screenfont has been tested with the public, including groups of visually and hearing impaired persons. There has been such general approval that the design team is confident that this new typeface will bring a considerable improvement in the legibility of text on screens.

Compatibility

The typeface is compatible with current screen generation technologies. An extended character set has been developed in March 2000. This includes characters that support the following languages:

Afrikaans, Albanian, Basque, Breton, Catalan, Croatian, Czech, Danish, Dutch, English, Esperanto, Estonian, Faeroese, Finnish, French, Frisian, Gaelic, Galician, German, Greenlandic, Icelandic, Irish, Italian, Latin, Latvian, Lithuanian, Maltese, Norwegian, Polish, Portuguese, Rhaeto-Romance, Romanian, Sami, Slovak, Slovenian, Sorbian, Spanish, Swedish, Turkish, Welsh.