An image forming apparatus includes a latent image bearing member, a charging unit, a charging power source, a latent image writing unit, a development unit, a transfer unit, a toner detector, and a controller. The controller causes a background fog pattern to be formed on a surface of the latent image bearing member. In addition to the background fog pattern, the controller causes a latent image to be developed to form a toner image used for position identification on the surface of the latent image bearing member. The controller identifies a time when the toner image used for position identification has entered a detection range of the toner detector based on a change in outputs of the toner detector to determine a time when each of sections of the background fog pattern enters the detection range based on the identified time.