Distance between dual 3D cameras — mimics human eye separation for stereo depth. Wider spacing = stronger parallax, narrower = subtler effect, higher comfort threshold.
When shooting with 3D cameras, the distance between the two lenses—the so-called interocular distance—determines the strength of the spatial depth effect. This works like our biological vision: the further apart your eyes are, the better you can estimate distances. A 3D camera simulates exactly that—and this is where it becomes critical for your storytelling.
In practice, this means: a small interocular distance (around 6–7 cm, similar to human anatomy) creates subtle, natural depth. This works excellently for drama, conversations, portraits—anything where the audience shouldn't be overwhelmed. If you increase the distance to 15, 20, or 30 cm, the stereoscopic effect grows exponentially. Objects practically leap out of the screen, the spatial separation becomes aggressive. This can be just right for action, for grand landscapes, for spectacle—in Avatar, for example, Cameron's teams consciously used variable distances to make fight scenes more intense.
The catch: too large an interocular distance quickly leads to visual discomfort. The audience has to strain their eyes too much to fuse the image. This is called vergence conflict—and it's a common reason why viewers leave the cinema after 20 minutes. So you have to think tactically: what emotional or narrative effect do you need? For closer action (close-ups, interiors), work closer to natural human geometry. For distant scenes or extreme perspectives, you can risk larger distances.
Practically on set, you have two options: either you work with a fixed stereo rig (both cameras rigidly mounted at a fixed distance), or you use variable systems that allow you to adjust between takes. Modern digital 3D rigs even allow for post-production adjustments—an advantage that classic stereoscopy didn't have. However, ensure that your convergence distance (the point where both images meet) harmonizes with your interocular distance. A large distance with incorrect convergence quickly becomes a trap for audience discomfort.