1. A vision system of a vehicle, said vision system comprising: a plurality of cameras disposed at a vehicle and having respective fields of view exterior of the vehicle; an image processing system operable to process image data captured by said plurality of cameras; wherein, responsive to processing of captured image data, said vision system is operable to synthesize a composite image derived from image data captured by at least two cameras of said plurality of cameras; wherein one of said plurality of cameras functions as a master camera and wherein said vision system, responsive to processing of image data captured by the master camera, determines operating parameters for the master camera; and wherein the determined operating parameters for the master camera are used by the other cameras of said plurality of cameras.