An image forming unit may include a capability of determining whether paper conveyed through the unit is bending. In some embodiments, an amount of bending of the conveyed paper may be determined. An embodiment of an image forming apparatus may include a paper feeding unit, an image forming unit, a skew correcting roller pair, a rotary member pair, sensors, signal processing units, and a control unit. A rotary member pair may convey a sheet to the skew correcting roller pair. Sensors may be disposed at various positions along the conveying path. In some embodiments, the sensors may include transmitting units and/or receiving units. These units may be positioned such that a conveyed sheet passes through therebetween. Signal processing units and control units may allow for the determination of the bending of conveyed sheets.