What is the principle of 3D photography?

The human eye is like a fully functional photographic system, with a zoom lens and a variable aperture, which can convert optical signals into electrical signals that can be recognized by the brain. In a two-dimensional image (such as an ordinary plane photo), we can "judge" the order of these objects in front of the background by using visual clues such as size and overlap provided by the objects, but we can't know how far they are.

Fortunately, we humans have two eyes, both of which are arranged on the front face, with an interval of about 65 mm When we observe an object, the images seen by the two eyes are slightly different because of their different angles. Our brains combine these two images to form a deep visual picture. This comprehensive treatment process is very rapid and seamless.

You can deepen your understanding through the following small experiment: take a sharp object such as a pencil in your right hand and your left hand, with the tips facing each other, then open your arms, close one eye (left eye or right eye, as you like:-), and try to align the two tips.

What did you find? This is because the picture seen by one eye has no depth before and after.

More importantly, the brain can judge the depth and distance of the same object according to the potential difference between the two received images. The farther away from the eyes, the smaller the potential difference, and vice versa. The schematic diagram shows how this process works: (when we look at the scenery at infinity) the position of the distant sun in the two images is (almost) the same, but the position of the nearby trees is different by 1/4 inches.

The same whole process is called stereoscopic vision, which comes from the Greek word "stereoscopic", meaning a shape or solid with three-dimensional structure. Stereoscopy refers to the method of putting two photos of the same object with slightly different angles together (with the left eye and the right eye respectively) to obtain a sense of depth, thus generating conventional stereo vision. Then (the most basic) stereoscopic photography is to shoot the same object from observation points with slightly different angles from the left and right, and then show the two photos in the same way, so that the left and right eyes can watch the photos with left vision and right vision respectively. Through the synthetic processing of the brain, a stereoscopic picture with stereoscopic depth can be obtained, which is completely consistent with the direct viewing of the subject by human eyes.