Image forming apparatus and image forming method

An image forming apparatus comprising:

• a transferred image bearer movable in a predetermined direction of motion;
• a plurality of image forming devices arranged in the direction of motion of the transferred image bearer, each of which including a pre-transfer image bearer to bear a toner image to be transferred onto the transferred image bearer;
• a toner adhesion detector disposed opposite the transferred image bearer to detect a toner adhesion amount of toner of the toner image adhered to the transferred image bearer;
• and
• a controller operatively connected to the plurality of image forming devices and the toner adhesion detector to selectively perform a multi-color image forming mode that forms the toner image with the plurality of image forming devices and a particular color image forming mode that forms the toner image with a particular at least one of the plurality of image forming devices,
• the controller to perform a primary image forming condition determination control to form the toner image for multi-color image density adjustment on the transferred image bearer with the plurality of image forming devices, detect the toner adhesion amount of the toner of the toner image for multi-color image density adjustment with the toner adhesion detector, and determine a primary image forming condition for each of the plurality of image forming devices in the multi-color image forming mode based on the toner adhesion amount detected by the toner adhesion detector and a secondary image forming condition determination control to form the toner image for particular color image density adjustment on the transferred image bearer with the particular at least one of the plurality of image forming devices, detect the toner adhesion amount of the toner of the toner image for particular color image density adjustment with the toner adhesion detector, and determine a secondary image forming condition for the particular at least one of the plurality of image forming devices in the particular color image forming mode based on the toner adhesion amount detected by the toner adhesion detector,
• the controller to perform the primary image forming condition determination control at a predetermined time and determine whether or not to perform the secondary image forming condition determination control based on the toner adhesion amount detected by the toner adhesion detector under the primary image forming condition determination control.