1. An imaging system comprising: an optical system adapted to form images on an imaging device, wherein said imaging device is capable of producing image signals of multiple frames, said image signals of multiple frames being read out of partial areas of said images on said imaging device; a read control portion adapted to select a read rule for said imaging device depending on sizes of said partial areas of said images on said imaging device, wherein a read start position is determined in accordance with the read rule; a portion adapted to generate a high-resolution image from said image signals of said multiple frames produced by said imaging device; and a portion adapted to make the read rule for said imaging device different for each frame; wherein the read rule for said imaging device is such that irrespective of said sizes of the partial areas, a total number of clocks upon reading of pixels is constant.