A CCD image sensor comprises photosensitive elements arranged in rows and columns, vertical CCDs each having vertical shift elements associated with respective ones of the photosensitive elements of a corresponding one of the columns, and a horizontal CCD comprising horizontal shift elements. The image sensor further comprises a transition region arranged between the vertical CCDs and the horizontal CCD. The transition region is configured to separate each of a plurality of signal channels provided by respective ones of the vertical CCDs into first and second parallel signal channels and to controllably direct selected ones of the parallel signal channels to the horizontal shift elements of the horizontal CCD in accordance with a designated readout sequence.