Depth is information, and some films are composed around it

The argument

This position begins by denying that stereoscopic presentation is decoration. Binocular disparity is one of the ways human vision establishes distance, and supplying it gives the viewer information that a flat image can only imply. Proponents argue that the difference is clearest in what it does to scale: the height of a drop, the size of a room, the distance between two figures and the volume of a crowd are all read differently when the eye is given the cue it uses outside the cinema. That is not an embellishment of the image but a change in what the image tells the viewer. From there the argument is that a format carrying information can be composed for. A director who knows the depth will be present can place the audience within a space rather than in front of it, use an empty foreground as deliberately as a background, stage an action across planes so that the eye travels through it, and withhold depth in some scenes so that its return carries weight. Proponents argue that this is a vocabulary rather than an effect, and that it is unavailable to a film made flat. The conclusion drawn is modest but firm. The claim is not that every film needs stereoscopic presentation, any more than every film needs colour or a moving camera. It is that a technique which changes how space is perceived, and which can be composed for, is doing work that nothing else does. On this account calling it unnecessary confuses the fact that films can be made without it with the claim that it adds nothing when it is used well.

Premises

Counter-arguments

Critics reply that the information argument proves too little. Disparity is one depth cue among many, it is weak beyond a short distance from the viewer, and the cues doing the work at cinema distances, such as occlusion, perspective, motion parallax and relative size, are all present in a flat image. They add that composing for depth has been possible for a long time and has produced very few films whose flat versions feel impoverished, which suggests the vocabulary is thinner than claimed. If a technique is defended on the grounds that it works when used well, critics argue, the defence needs the examples, and the audience's willingness to watch the flat version of almost anything is the relevant evidence.

Rejecting the premises

[Rejecting P1] Disparity operates over a short range and contributes little at the distances involved in watching a screen, so supplying it adds less information than the premise suggests. [Rejecting P2] Scale and volume are already read from perspective, occlusion and motion, and viewers of flat films do not misjudge the height of a drop or the size of a room. [Rejecting P3] Composing for depth has been available for a long time without producing a body of work whose flat versions fail, which is what the premise would predict. [Rejecting C] At most it follows that the format can be used expressively, not that a film is missing something without it.