1. An image forming apparatus comprising: a rotation member configured to form a toner image on an image carrier based on image information; a first acquisition unit configured to acquire density variation cause information about a cause of density variation occurring in a sub scanning direction of an image, which may occur due to rotation of the rotation member; a correction unit configured to correct the image information according to the information about the cause of the density variation acquired by the first acquisition unit; and a second acquisition unit configured to acquire indirect density variation information, which indirectly indicates a level of the density variation, wherein the correction unit is configured to set a level of correcting the image information corresponding to the density variation cause information based on the indirect density variation information without detecting, from the formed toner image, a level of the density variation corresponding to the density variation cause information.