Ensure that the text is readable by all users including those with limited vision or reading disorders

Rationale

People with vision impairments may have difficulty reading text that is not in large, clear static type and contrasted well against the background.

Colour.... (blue on blue) can make it hard to
read.

Guidelines survey respondent.

People with colour vision deficiency can have problems with particular combinations of colours. Similar problems may occur within graphics. In addition to the text and graphics itself, poor layout or the existence of moving content that distracts the eye can make reading difficult. Some of these problems also affect people with reading disorders, even if their vision is perfect.

Directions and techniques

Ensure that text and graphics appear within the area of the screen that can be clearly seen (high priority)

All informational text and graphics should appear within the title safe area. That is the visible area where the text will not be cut regardless of the over scan (margin of the video image that is normally not visible) of the television used.

Use a clear typeface and lettering for easy on-screen reading (high priority)

To ensure readability, use a screenfont a typeface that has been specifically designed for viewing on television displays at typical viewing distances.

The text size should be sufficient to be readable across a wide range of visual acuity. The recommendation of DIGITALEUROPE in the Industry Self-Commitment to Improve the Accessibility of Digital TV Receiving Equipment Sold in the European Union is to use 24 line minimum for body text and 18 minimum for upper-case text on a 576 line display.

Italic, underlined, oblique, condensed, all upper case or fancy fonts can cause problems for some people and should be avoided in favour of plain, mixed case lettering.

Blinking or moving text or graphics should be avoided as it can be difficult to track and can distract the eye, making it difficult to read other static text.

Carefully choose colours and colour combinations (high priority)

A sufficient contrast between text and its background is required for it to be easily distinguished and read. Dark colours on a light, non-patterned background or light colours on a dark background can both be used. Combinations of red and green should be avoided since they can be difficult to differentiate for people with the most common form of colour vision deficiency. Saturated or bright colours such as pure white or absolute black should also be avoided. The European Industry Self-Commitment recommends that colours be limited to an absolute maximum of 85% saturation to avoid text appearing to distort or flicker.

Graphics should be treated in a similar way to text, with similar requirements for contrasts between adjacent, overlaid or background colours.

Information should not be presented using colour alone. There is nothing wrong in using colour to indicate meaning, as long as it is not the only indication.

Adopt a layout that makes reading easy

In cases where there is a lot of text, for example the introductory or background text that appears at the beginning of some films or programmes, use left-aligned text in preference to centred, right-aligned or justified text. Left-aligned text is generally easier to read.

Use short paragraphs in preference to long ones.

Avoid using multiple columns as these can lead to content comprehension problems or disorientation for some users. If multiple columns are appropriate, to indicate logical relationships for example, ensure there is a sufficient margin between columns and an adequate column width.

Text should have adequate line and paragraph spacing. Recommended line spacing is at least half the height of the text. Recommended paragraph spacing is one and a half times the line spacing.

How you could test for this

To find out whether text is readable, it is necessary to run tests with a wide range of viewers, including people with a range of vision impairments and people with reading disorders such as dyslexia. These tests can be carried out in the viewer’s own home and could be run as a questionnaire in which the user has to report back the information they see on the screen, with feedback about how easy it was to read.