The novice photographer asked: What is a dog's head?

Dog heads generally refer to those shots with average picture quality, which may be difficult to distinguish. You can look at the standard directly: Canon's advanced lens is marked with a red circle, Nikon is a gold circle, and you can understand it as a dog's head without it. Look at the picture below. (Note: Except for the fixed-focus lens, the picture quality is very good even if there is no loop. )