This is an example of symmetry because if this were cut in half vertically, there would writing, one black colored circle and half of the red batman symbol would be on both sides of the poster. The symmetry provides balance to the poster in that the images create the Joker's face.
This is an example of asymmetry because Iron Man's body is mostly on one side of the movie poster and the writing is mostly on the other side of the poster. The asymmetry still provides the poster with balance because although one side is mostly his body, the other side is his outstretched hand (a point of focus that was meant to be emphasized).
