Blind Presenter: Apply Font size to All Slides

I regularly create educational materials for learners with visual impairment through the use of sound recordings.

I can't imagine the challenge for blind people creating material with Keynote. I hope the following remarks are helpful as a starting point if nothing else.

I know, the minimum font size one should use is 30.

Actually the font size must be determined by the end product, who the viewers are and the environment where the presentation takes place. Text at 30 point shown in a lecture room is far too small to be legible, 30 point may be suitable when sitting at a display 2 feet away.

How many characters will fit in a line?

This again must be determined by the end product and not how many characters can be shown. What is actually important, is the number of words on a slide, not the number ofcharacters.

The number of words that are easy to read on a projector screen in a small training room will be different to the number of words that are easy to read in a web browser on a computer display.

The accepted rule for text created by professional designers in Broadcast Television and for projected presentations is a maximum of five words per line and 6 lines per page, a maximum of 30 words per slide. For example, in Europe there are legal requirements placed on television broadcasters for viewers to read text easily.

I have copied text from a text document into a slide; of course, the font and size are not the same. Can I make sure all fonts and sizes stay the same throughout the presentation?

Use Paste and Match Style from the Edit menu, the keyboard command is shift option command V

the table is legible but could be much, much bigger. Is there a way to auto-align a table so it fills the slide?

Select the table then increase the font size to the required amount.

I am happy to answer questions about my reply.

I mostly give workshops in front of max. 50 people, i.e. small seminar rooms. Would an average 36 pt size work as a rule?

No Im afraid not, the minimum size for 50 people would be 80 point.

A legibility test consists of viewing the screen at the maximum distance a viewer would be placed. In the situation of fifty people, the arrangement would be in five rows of ten people and viewing from the back row requires 80 point text as a minimum.

Yes, using the paste and match style is pasted from the clipboard.

I asked about characters per line because

Legibility of text is assessed by the number of words on screen and not by characters. This is because when people read, the eye scans words, not individual characters.

Good luck with your presentations, feel free to post any further questions you have.