The 40D can display the autofocus point (or points) that was active when the picture was taken as a tiny red square when the full information display is chosen for playback. (Some users mistake the red square in the playback thumbnail as a “hot” pixel.) Choose AF point disp. in the Playback 2 menu and select Enable or Disable. There is little reason not to view this information, so most leave this setting switched on at all times. There’s more about choosing autofocus points in Chapter 5.