A method and apparatus for forming an image reduce the processing load on a video controller. A CPU causes a counter to start counting the optical beam detection signals of a photodiode in accordance with a signal which indicates the leading edge of a sheet of recording paper received from a TOP sensor. Comparators compare the count value issued from the counter with the values set by the CPU at registers. Based on the comparison result, an F/F sets Q output. Thus, a BD signal is issued through a gate during a period specified by the values set at the registers. The use of the BD signal reduces the processing load on the video controller which generates and transfers an image signal.