All camera lenses will get worse and worse after long use. Mainly because: first, there will be dust between the final lenses, and there will be professional lenses with higher sealing; Second, the lens is worn, mainly because the coating on the lens surface will be worn and damaged every time it is rubbed; Third, the existing lenses all have auto-focusing photosensitive elements, which will age, leading to more and more inaccurate focusing; Fourth, because of focusing and zooming, the lens sleeve will become looser and looser, and the focusing and imaging quality will decrease; Fifth, the lens will always shake or shake to a certain extent, which will affect the quality of focusing and imaging more or less. As for whether Sima's lens is "a bull's head in one year, a dog's head in two years", it depends on the degree of use and protection. High use and poor care for lenses may lead to a rapid decline in the overall quality of lenses; If you don't use it often, take good care of the lens, which can greatly extend the life and overall quality of the lens.