Photography Who can tell me what is focus, focal length and focus?

In a photo, the clearest part of the image is the focus.

The focal length is the distance from the lens center to the imaging plane (such as basement membrane or CCD).

Focusing, focusing includes manual focusing and automatic focusing. Focusing is a way of focusing by twisting the focusing ring and adjusting the camera lens to make the pictures clear. Simply put: it is to make the objects seen in the lens clear. The ultimate goal of "focus" is "focus".

Zooming in or out of the subject is called zooming.