Avatar 2 is possibly the most sought-after sequel to many movie series within the last decade and now, thanks to YM Cinema, we get to share details in how it was shot. The world of cinema 3D is a weird beast, would would think they would all be shot on 360 degree cameras, but in reality they usually 2 camera rigged together and set to record both both left and right "views" so they can be assigned to the corresponding eyes, I have even seen 4 or even 6 cameras all rigged together to produce a 3 dimension image in post when they wanted to great vast 3D vistas.
With Avatar 2 however, a specially made 3D stereoscopic beam splitter system was used in-toe with the Sony Venice Rialto extension unit, which is properly called the Sony CineAlta Venice 3D.
For Avatar's sequel Director James Cameron, used multiple Sony Venice cameras have been paired in various 3D stereoscopic rigs using the Sony cabling system, the only part of the Venice carried on the rig was the image sensor optical blocks (Rialto), significantly reducing on-board camera weight to about three pounds per sensor block, as stated by Sony.
By lowering the weight and improving ergonomics, Cameron earned the ability to shoot with greater flexibility and freedom and with the recent Avatar 2 trailer release. 3D rigs are known as mirror rigs or beam splitter rigs, the whole idea with 3D is to capture left and right-eye images and then superimpose them on the screen so that we get the perceived impression of depth within the picture. The way it can be achieved is by using two cameras one for the left eye and one for the right eye.
Furthermore, it’s quite important to get the distance between those cameras correct for each scene and this is where a beam splitter comes in really handy. The image from the top camera is reflected off the mirror which is a 45 degrees image from the horizontal camera that shoots through the mirror. By adjusting these cameras from side to side you can actually make the distance between them correct for the particular 3D depth of the scene.