It is largely caused by the characteristics of the camera. When using a wide-angle lens, the shape is distorted, and the nose and cheeks near the lens seem to bulge and swell. When shooting with a telephoto lens with a long focal length, the distance difference between different parts of the face will be relatively reduced, and the face will appear relatively flat. In other words, the lens used in shooting has different focal lengths, and the images taken will change greatly.