Why is the ultra-wide-angle lens also called a fisheye lens?

Among the human sensory organs, the most perfect and exquisite ones are the eyes. The camera is made to simulate the structure and working principle of the human eye. However, the human eye also has shortcomings. If calculated based on the visible standard, the viewing angle of the human eye is about 150°, but calculated based on the standard of being able to see clearly, the viewing angle is only about 5°.

In the animal kingdom, fish eyes have the largest viewing angles, some as large as 160° to 170°, and even larger ones.

After studying fish eyes, scientists imitated fish eyes and made an ultra-wide-angle lens with a viewing angle of 180°. This kind of lens is called a fisheye lens. The "fisheye camera" made with this kind of lens can "panoramic view" the entire space at once and project it onto a small film. At this time, the image becomes circular as seen by a fisheye, so the range that can be photographed with this fisheye camera is much larger.

Fisheye lenses can not only be used for ordinary photography, but also have many special uses. When taking underwater photography, due to the large angle of view of the fisheye lens, you can get as close as possible to the object to be photographed, which reduces the distance between the lens and the object being photographed, making the underwater photos very clear. When people use a TV to monitor a certain scene, due to the size of the viewing angle, an ordinary photographic lens must be attached with a device to make the lens scan back and forth continuously. After replacing it with a fisheye lens, the entire scene can be seen clearly at a glance.