A post production process where negative and positive parallax convergence are adjusted. This is not only a creative tool used to place objects on the Z axis but also a way to ensure that stereoscopic content can be comfortably watched on the screen size it is intended for. For example, in a post suite the director may be viewing a film on a small projection screen but the final delivery format may be a large theater or IMAX.
In practice the eyes have little ability to diverge (up to one degree is considered the rule of thumb) and this is especially a consideration in depth grading for very large screens with positive parallax images, where the distance between the left and right representations of an image may be very widely spaced.
Sometimes the term Depth Budget is used to refer to the allowed combined value of positive and negative parallax and expressed as a percentage of screen width.
See also: Parallax