If we take a picture using a single lens, the pictures should be viewed with a single eye as well. Not convinced? Close one eye when looking at a photograph (or even while watching the TV), and you will instantly feel the sense of depth. This happens because the brain is no longer receiving the other eye’s visual to identify the image as flat — and it reconstructs the volume picture as best it can.

Nature has given us two eyes so that we may perceive the world around us in three dimensions. This perception can be emulated by flat images, whether still or moving, if they somehow carry visual information for both eyes. It is achieved by so called stereo-photography.