The problem is that the autofocus can not adjust correctly. There can be more than one solution.

1. Try forcing the lens to rotate a fraction of a inch. This will sometimes help the problem. Or simply move the switch from M to A on the lens.

2. Try to switching to a single of the 11 auto focus points. Then try if there are specific points that are the problem.

This is done by selecting in the menu of your camera to the points. Then focusing on a single object with a background far away. Try focusing on the object then on the background. If this is possible the autofocus point is fine.

3. If all auto focus points are fine, try updating the firmware or cleaning the sensors inside the camera behind the mirror. If a one or more points are out of order, also try cleaning the sensors behind the mirror.

4. Detatch the lens from the camera, by applying pressure on the release button and twisting the lens so it can be released. See picture

5. Set the camera selection wheel to manual (M), see picture

6. Turn the camera on, and start the liveView format. This will flip op the mirror inside the camera.