Is it possible to focus your vision in and out

Question

Is it possible, like in sports when you have to track things, to focus your vision in and out. I read in an article on wikihow that to track and copy movements you must learn to focus your vision. Here is the article: http://www.wikihow.com/Track-and-Copy-Movements-With-Your-Eyes

Answer 1

Sure! Have you ever seen those pictures where they ask you to focus past the picture and then some 3D image will pop out of the picture? Thats basically what you're doing. You're focusing your eyes past the plane of the picture.