The reason? Probably the fact that they really don’t think about it from the audience’s perspective. Or don’t know enough about the technology. In this particular case, the presenter was using dark blue letters on a yellow background – exactly the opposite of what he should have been using.
The problem with a light or white screen is in the light from the projector. A white background can be like looking into a headlight – hard on the eyes. That’s because the projector light is bouncing off the screen right back into your eyes. On top of that, the human eye is attracted by light. So the natural reflex is to look at the light background and not the text.
And the example above is about as bad as it gets. Not only does the lighter background attract your attention, but the stadium picture fights your ability to read the text. It is simply too busy. In actual fact, when this slide is projected, the stadium usually disappears. Typically, you’ll lose 10% of the contrast – enough to make this projected background totally white!
Consider this. If you want to attract the eye to a section of the slide that’s really important, you’ll want to make it the lightest element on the slide. Television directors have used this trick ever since the medium was invented. Cut to a new shot and the eye will instantly seek out the lightest area and that’s what it will see first. That’s what will be remembered long after a darker element – in fact, the darker element might get missed altogether! If you want to attract attention to a certain word during the time a slide is up, fade it on . . . and make it white or yellow. Your audience will instantly be attracted to it and, coupled with the words you utter at the same time, it’s an incredibily powerful way to reinforce your point.
The rule: light on dark (not necessarily black) with as much contrast as possible. A dark background with yellow or white text is the best way to go. Now that still leaves lots of room for creativity. The challenge is not to let the creativity interfere with your audience’s ability to read the text – the main reason you have text up there in the first place!