A linear image sensor comprising a linear array of photosites adjacent to a charge coupled device (CCD) that is preferably a two phase CCD with a transfer gate between the array of photosites and the CCD with an output amplifier situated at the end of the CCD. At least one of the phases is divided into a split phase having two sets of electrically isolated gates that can be operated as a single phase or as two independent phases. The linear sensor operates in a reduced resolution mode by summing charge packets from adjacent photosites wherein the split phase functions as essentially two alternating phases with the phase that is not split being held at a D. C potential.