Aside from the visual clues you mentioned, I like to use the example of a screen door or vertical blinds. Most people have the experience of inadvertently focus

Aside from the visual clues you mentioned, I like to use the example of a screen door or vertical blinds. Most people have the experience of inadvertently focusing on these things a bit wrong and "feeling" that the objects are much closer or farther than reality. Computer vision can make the same mistakes easily, and in fact can often perform much worse than human vision. Backlit scenes are difficult, frontlit scenes are more difficult, and scenes with a lot of repetition and few large features are almost impossible. Examples of almost impossible scenes are backlit beach on a sunny day and cloudy day while skiing, and all kinds of conditions while driving, such as frontlit or sidelit with a wet road.