Patent ID: 8160465

Claim:
An image forming apparatus, comprising: a transferring unit to form a visible image on a print medium, the transferring unit having a transfer region at which the visible image is formed; a bias supplying unit to supply bias to the transferring unit to form the visible image on the print medium; and a controller to control the bias supplying unit to supply bias to the transferring unit such that a magnitude of bias applied to the transferring unit changes from a first bias level to a second bias level after a leading edge of the print medium passes through the transferring unit and subsequently changes to a third bias level before a trailing edge of the print medium passes through the transferring unit, including: a first mode where the controller controls the bias supplying unit such that the second bias level applied to the transferring unit is higher than the first bias level and the third bias level is higher than the second bias level, and a second mode where the controller controls the bias supplying unit such that the second bias level applied to the transferring unit is higher than the first bias level and the third bias level is lower than the second bias level, such that the controller selects one of the first and second modes based on at least one of an attribute of the print medium and an environmental factor.