Abstract: A sheet behavior monitor for a sheet processor includes: a folding machine processing a sheet; and a camera taking an image once for each signature (Wb) folded by the folding machine. The camera takes every image at a folding machine rotation phase different from that of the image immediately before taken.

Abstract: In a printing press including a printing section to print patterns, a register apparatus captures an image of register marks printed in the printing section, and causes positions of the patterns, which are to be printed in the printing section, to be in register on the basis of positions of the register marks in the image. The register apparatus comprises: a front surface camera or a back surface camera for capturing an image of an edge of a print sheet together with the register marks, the print sheet already subjected to printing in the printing section; and a first-color register adjustment mechanism, a second-color register adjustment mechanism, a third-color register adjustment mechanism and a fourth-color register adjustment mechanism for adjusting the positions of the patterns to be printed in the printing section, on the basis of the positions of the register marks in the image and a position of the edge of the print sheet in the image.