Two offset cameras mimic binocular vision, creating stereoscopic depth for viewers. Demands synchronized rigs, matched lenses, color correction, and careful convergence management.
Two cameras, minimally offset – that's the basis. The distance corresponds approximately to the interpupillary distance, about 6.5 centimeters, sometimes larger for more extreme depth effects. Each camera captures its own image, both are recorded synchronously. In the cinema, each eye then sees its own image – separated by polarizing filters, shutter glasses, or red-cyan anaglyph technology. The brain combines the two perspectives and constructs depth, where in reality only two flat projections are running.
On set, this means stress for the camera department and editing. The rigs – usually two synchronized digital cameras on a mount – weigh tons. Every movement must be absolutely parallel, otherwise the viewer gets a headache. The convergence point – the point in space on which both cameras focus – is constantly readjusted. Too close to the lens, the depth appears artificially exaggerated; too far away, the image flattens out. Good 3D camera work never lacks thought before shooting.
In post-production, new problems await: Both takes must be precisely synchronized, and each plate requires separate color correction and VFX work. A simple editing plane becomes a double editing task. The depth of field also behaves counterintuitively – in 3D, less focus is often required than in 2D film to avoid eye strain. Extremely deep focus planes lead to involuntary viewer exertion.
Practically, 3D works best at a controlled pace: slow camera, thoughtful cuts, moderate depth of field. Hectic action sequences often appear tiring. Many early 3D films ignore these rules – the result: ticklish eyes after two hours. Those working with 3D stereoscopy must not surprise the viewer, but guide them – spatially, slowly, thoughtfully.