PowerPoint Mistakes -- from a usability standpoint

I saw a presentation today. Some of its fonts were really tiny.
That prompted me to google "powerpoint mistakes". Got many hits, including this funny and informative YouTube video by Don McMillan.

Interestingly, these sources often only tell you what to, or what not to do, but don't really tell you why.
For example, some would tell you "don't read the slides", "use a minimal font size of 24", "don't use more than 7 bullets on a slide", "don't use dark color text on dark background", etc.

But what are the common rationale behind all these dos and don'ts?
Usability -- that is whether it is easy for your audience to "use" (read, understand, see, etc.) your slides.

If you think about your slides' usability as the first priority, then I expect you can naturally fix many of your slides' problems. For example, you won't:

  • use fonts smaller than 24, because audience in the last row of a room can't see the text
  • use more than 7 bullets, slide gets visually complex, straining your audience's eyes
  • use dark color text on dark background, because your audience will find it hard to read
  • read slides, because your audience will find you boring,
  • and the list goes on...

I think it's much better to only remember one thing -- the principle of good slide usability -- rather than having to remember a laundry list of dos and don'ts.

Usability is one focus of within the research area of Human-Computer Interaction. I think it also applies to slide design.