focus, is not duplicated and therefore the illusion of depth is incomplete. There are two main elements of stereoscopy that are unnatural for human vision: (1) the mismatch between convergence and accommodation, caused by the difference between an object's perceived position in front of or behind the display or screen and the real origin of that light; and (2) possible crosstalk between the eyes, caused by imperfect image separation in some methods of stereoscopy.

Although the term "3D" is ubiquitously used, the presentation of dual 2D