Improved correlation techniques employ data from forward and reverse correlation to identify valid correlation peaks, enforce symmetry in correlation peaks, andor combine forward and reverse correlation data. A length of the conveyance path extending from a downstream edge of the imaging range to the nip is longer than a maximum length of the recording medium usable in the image forming apparatus to prevent a leading edge of the recording medium from being sandwiched by the second discharge member when the carriage performs last scanning movement. Various closing members are shown, some of which feature magnetic members.