Incorporating a few basic techniques into your presentation slides will go a long way towards assisting accessibility for your blind and partially sighted users.
Rather than just produce your presentation ad hoc from blank slides you can create a much more consistent and accessible result by using built in templates.
Presentation software generally provides a range of preset templates from which various types of slides can be created. Slides can be produced which are text only, text with graphics or other multimedia content.
Why use templates?
From an accessibility point of view templates provide a structure to the presentation which aids navigation particularly for screen reader users. You can choose an appropriate template depending on whether your slide is text only or text with graphics or other multimedia content. It is important to use these templates as the structure of the presentation is automatically maintained.
An outline view of your presentation will very clearly show this structure which significantly aids navigation. This enables screen reader users to more easily find their way around your presentation.
Slides containing text
What do you need to consider when adding text to your slides?
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Text should be as concise as possible whilst still being able to convey the required information. A recommended optimum for guidance is up to six lines of information per slide.
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Important text should ideally be as large as possible and in a clear font such as Arial. As a general rule a minimum font size of 32 point is recommended for maximum legibility.
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Try to avoid where possible applying italics, underlining text or overusing block capitals. All of these embellishments can make it more difficult for a partially sighted user to read the text. However, small amounts of important text can be emboldened to provide emphasis where required.
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Apart from headings which may be centred, try to leave text left aligned. Right aligned or centred text has lines starting at different points across the slide making it more difficult to navigate.
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Try to maintain good contrast between the text and the background colour. Try to be consistent with the level of contrast throughout the presentation.
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Bulleted or numbered lists can help to break up the text and make it easier to understand.
Graphics in slides
It is a mistake to assume that blind and partially sighted people are not interested in the information that can be conveyed pictorially or graphically.
Try to avoid having your graphics located behind or overlapping the text though. Whilst this can create visually appealing slides it can cause confusion for partially sighted users where text and graphics are not clearly separated. If the graphics are there to convey meaning why hide them behind your text?
If images such as charts or graphics are essential to your presentation you can add a caption to describe the important points.
eg. 'Recycling Pie Chart' does not convey any meaning but 'Chart showing 20% increase in glass recycling since April 2008' does.
Further information on accessibility for presentation software can be found on the Projected presentations, Multimedia in presentations, Transitions and effects, Producing handouts and Providing accessible formats pages.