The photographer photographed graduation photo, a ninth-grade student, and found that two students were not in the camera. At this time, the cameraman retreated and put the mirror.

In the process of exploring the imaging law of convex lens, when an object approaches the convex lens from a distance, the image formed by the object gradually becomes larger and farther away from the convex lens.

So at this time, to reduce the image, the convex lens should be gradually away from the scene, that is, the camera should be away from the students and the lens of the camera should be shortened.

So the answer is: backward.