Why is the camera round but the photos taken are square?

Why is the camera lens round but the photos taken are square? This is a very interesting question. It involves several aspects of knowledge.

As we all know, our common photo format is 3:2, which is different from the imaging of the lens.

This is the circular image formed by the lens and the recorded photo specifications

If the exposure range is forcibly expanded, the photo will have dark corners.

Vignetting in photos is often caused by insufficient field of view of the lens.

Why is the lens round and not rectangular? This is because the lens is composed of a lens intercepted from the surface of a sphere, and the light rays are symmetrically gathered to form an image with the center point as the origin of the coordinates.

Although the light path diagram we see in books is purple

But the actual lens is purple

If the lens is not symmetrical at the origin, but symmetrical along a horizontal line, the lens It will become a part of the intercepted cylinder, and what everyone sees is not a clear image, but one-dimensional information like a barcode.

Semi-cylindrical lens

Image that loses the y-axis

The lens is a cross-section of a sphere, so it is naturally circular. At the same time, the processing and use of the lens barrel, Whether it is cutting processing or rotary zoom, the round shape is a good choice. And there is another very important reason. In many previous cameras, the lens was fixed in a spiral and had no accurate direction. Square or other special-shaped lenses cut like spectacle lenses could not guarantee the angle of the picture.

Then why are the photos square? This is because, like other traditional civilization carriers, there are historical issues caused by film and photo paper cutting. In the days of film/paper silver salt photography, both film and paper were cut from large sheets of material. The most reasonable way to cut a plane is a regular quadrilateral. If it is cut into a round shape, a lot of scraps will be produced, which is not conducive to collection and binding.

This is the remnant of circular cutting

In fact, if the content of the picture is extremely important and is much higher than the cost of recording, the photo can also be circular to maximize utilization. What the camera captures. Such as cosmic exploration or photomicrography. It's just that when it is displayed on paper or a monitor, a rectangular frame is put in it to facilitate our management and browsing.

In microscope photography, the effective picture is circular.

After historical evolution and elimination, the phenomenon we see has emerged. The lens is round and the photo is square.