Why do most movies only have the middle one, instead of full screen, such as TV series?

It's a cover-up of a movie, and it has a history.

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A cover-up movie is also called a "fake widescreen movie". Some people may not be clear about it. When shooting a wide-screen film, a special deformation compression lens is needed to compress the scene horizontally into a thin and long deformation image. During screening, the original horizontally compressed image is stretched horizontally in proportion by using the deformed projection lens with reverse compression. In this way, it will produce a wide-screen movie with a wider field of vision and a stronger sense of reality.

In order to change and omit the tedious photography and projection of the optical deformation principle, on the basis of the ordinary 35cm screen size, one piece is covered from the top and one piece from the bottom to form a wide effect. In this way, although an unimportant edge part of the picture is lost, after enlarging the screen reduction size, the wide screen effect appears, so it is simple and applicable. It omits the use of anamorphic optical system for photography and projection. When shooting this kind of film, we only need to shoot it through the ordinary cinematographic lens, and add a limiting frame in front of the camera lens, so that the upper and lower sides of the ordinary screen are partially covered, thus changing the frame ratio. When projecting, we only need to reduce the height of the door hole of the projector, so that the width-height ratio of the screen can reach 1: 1.66, which is the width-height ratio of the screened film in China, so that we can receive the effect of wide-screen movies. In recent years, due to the progress of film technology and the increase of camera motion range, people deeply feel that the field of vision of ordinary screens is not wide enough when shooting large scenes, while that of general wide screens is not as ideal as that of ordinary screens when shooting close-ups and close-ups of people, so this kind of screen ratio with the advantages of both screens has been found.