In 1838 Charles Wheatstone created the Stereogram. Originally he was working on stereo binoculars but along the way he discovered that you could capture and reproduces 3D Depth using the same techniques as in the binoculars. Ever since then 3D has come in and out of fashion.
3D has not only been possible with digital. 3D has been around even with film cameras. So whats different about 3D in Films today. The Truth is that most Films today are not filmed in 3D. to get a film in 3D if very difficult because you have to have two camera that are synced together or “Genlocked”. this means that the cameras are 100% synced. each frame is taken at the same exact time, the Shutter speed is exactly the same, the aperture is the same and the lens is the same. this is the easy part for the camera. The hard part is eye distance. in order to film in 3D and make a movie that does not give you a headache the distance between the center of both camera lens has to be the same as the humans eye distance from left to right.
This is nearly impossible with professional grade gear because the camera body it’s self is wider than that that distance. So you can’t put two cameras side by side. A solution to this is a mirror rig. This is when through mirrors you can angle the cameras so that they look into the mirror and what they see is eye distance apart from each other. but this makes the camera very heavy and difficult to move.
So most studio today to post-processed 3D. this process as also been evolving. For the first films to use this technology the computer did all the work. for each frame of an image computer world look at each pixel. the brighter the pixel and the more variety from the pixels next to it would determine the clarity of that pixel . Now based on how clear that pixel was meant that that pixel was closer to the camera. the computer would then calculate to make it closer in 3D by creating two images. one with that pixel slightly to the left. and another with that same pixel slightly to the right. the computer would calculate this for every pixel in the frame.
Unfortunately this produced a lower quality 3D extrapolation, that made the images look swim-y and wavy, as well as nauseating.
Today the computer and people do the work. 3D extrapolation is made now with depth maps. this is where a human takes the frame and draws on it. the person uses black for the objects in the far back. and white for objects closest. the computer then takes that black and white sketch and re-applies it to the image, again adjusting the pixels to the left and the right, only this time based on the depth maps drawn by hand from a person.
But does it compare to a real film shot 100% in 3D. some can’t tell the difference. Some can. Personally I don’t want to see a film that has been post processed to be in 3D, there always quality loss. Yes the extrapolation is better,but its still not there yet. On that note I do like 3D films shot with 3D cameras. I’v worked with several 3D Cameras and the amount of depth you get from a real 3D Camera does not compare to post processed 3D.