Stereoscopic 3D system using two side-by-side cameras — mimics human binocular vision through offset imagery. Industry standard for digital 3D cinema since Avatar.
Two cameras mounted side-by-side, each with identical focal length and sensor — that's the foundation. The horizontal distance between the lenses (the interaxial distance) is typically 65 millimeters, thus mirroring the distance between human eyes. Each camera captures the subject from its perspective; in cinema, the left eye sees the image from the left camera, and the right eye sees the image from the right camera. The brain merges these two slightly offset images to create spatial perception — just like with natural vision.
On set, this functions like two synchronized productions simultaneously. The cameras run in timecode lock, focus must be identical for both lenses, and exposure follows the same lighting setup. This sounds simple but quickly becomes a logistical challenge: each focus puller juggles two distances in parallel, the camera assistant must monitor both sensors, and the rig itself — usually a rigid aluminum construction — requires space. In tight interiors or for close-up shots, it becomes critical; one then has to switch to variable interaxial distance or resort to a single-camera conversion.
In editing, the real work begins. Both takes must be synchronized frame-accurately — a lost frame leads to cross-talk between the eyes, which the viewer perceives as a headache. The convergence — the point on which both images are focused — is corrected in post-production. It can be shifted afterward, manipulating depth perception: push the convergence backward, and the viewer feels like they are inside the space; push it forward, and the action jumps out of the screen. This is not a bug but a feature — and one quickly learns not to overdo it.
Since Avatar, this method has established itself as a production standard because it is technically reliable and builds upon existing camera infrastructure. Alternatives like lenticular or single-chip 3D find their niche, but for large-format cinema productions, Natural Vision 3D remains the method of choice — if the budget and schedule allow.