What happens if the camera is focused, Zhihu?

The camera adjusts the focal length of the lens. The longer the focal length, the smaller the viewing angle of the lens and the narrower the background range, which is convenient and simple to sort out the background. The longer the focal length, the greater the imaging of the distant subject, which allows us to shoot the distant subject. The lens with the same aperture value and long focal length is more likely to get a blurred background. On the contrary, the shorter the focal length, the larger the viewing angle, the smaller the imaging of the distant object and the larger the depth of field.

I hope to adopt.