1. A mobile camera system including at least first and second cameras mounted on a mobile body and a camera control unit that combines images photographed by said first and second cameras, wherein reference data obtained by the first camera apparatus is transferred to the second camera via said camera control unit, signal processing is performed in the second camera on the basis of the reference data transferred to generate a corrected image, and an image from the first camera and the corrected image outputted from the second camera are combined to output a combined image; wherein the second camera performs adjustment of luminance and colors according to the reference data, and further wherein the camera control unit sets the first camera apparatus as the reference camera and image reference data is transferred from the reference camera to the remaining cameras, and further wherein the camera control unit selectively changes a source of the reference data from the first camera apparatus to a different camera apparatus; and wherein a third camera receives the reference data obtained by the first camera and a fourth camera receives average image signal processing data used by the second and third cameras for use as master image signal processing data for the fourth camera.