TL;DR – never use white text on a black background in your slides.
This post has been a long time coming. Every conference I go to, there will be at least one (and more often ten or twenty) presentations that use white text on a black background. These slides range from hard-to-read to outright illegible and in particularly bad set-ups are so visually painful that I have to close my eyes or turn away from the projection screen. Even conferences that provide advice on designing accessible presentations nod at the “make slides high contrast” but are silent on the white text issue. So! Here it is.
- approximately half the population has some degree of astigmatism
- white text on black backgrounds creates a visual fuzzing effect called “halation”
- halation is known to reduce readability of text and is particularly bad for people with astygmatism
The visual aids:
So please, everyone, strike white text with black backgrounds from your color repetoire, the same way you’ve removed color combinations that are illegible to color-blind people. It’s not a question of preferences, it’s an accessibility issue.