Patent ID: 8862000

Claim:
An image forming apparatus comprising: a conveyance member configured to be rotated; a detection unit having a detection area on the conveyance member and configured to output a detection signal according to a mark for image formation condition correction, which passes the detection area; an image forming unit configured to form a print image on the conveyance member or on an image forming medium conveyed by the conveyance member when printing on the image forming medium, and configured to form the mark on the conveyance member or on an image forming medium conveyed by the conveyance member when detecting the mark by the detection unit; and a control device configured to change at least one of a printing reference position and a mark reference position such that an offset amount between the printing reference position and the mark reference position becomes larger as an angle difference between a sub-scanning direction of the image forming unit and a conveyance direction of the conveyance member is larger, wherein the printing reference position is a basis of determining a formation position of the print image in a main scanning direction of the image forming unit and the mark reference position is a basis of determining at least one of a formation position and a size of the mark in the main scanning direction.