The person photographed by the camera is particularly fat

Answer: This is due to the perspective relationship.

As we all know, one way our eyes can sense distance is to use the relative size of objects. The brain will tell us that objects appear smaller when they are far away, and the farther away they are, the smaller they appear.

In photography, the same method is used to identify perspective relationships. Distant objects appear smaller than nearby objects of the same size. Take all the photos from the same location and then zoom in on the same part of each image, with the goal of getting equally sized images on the photo. Finally, regardless of the focal length of the lens used, you will not see any difference in perspective in any of the photos. The reason is that all photos are taken at the same distance, that is, the distance from the subject to the lens is the same.

Since the subject appears larger as it gets closer, when shooting close up, other parts close to the lens appear disproportionately large. This distortion occurs when the subject is very close to a certain extent. The closer to the subject, the more severe the distortion. Portrait photography precisely enters the distortion distance range of the lens because it is hoped that the subject will fill the frame. In fact, this distortion will occur no matter what lens is used at the same distance.