1. A method of image enhancement for a vehicle vision system, said method comprising: (a) providing a camera at a vehicle so that the camera has an exterior field of view; (b) providing a processor operable to process image data; (c) capturing multiple frames of image data with the camera; (d) executing a first brightness transfer function on a current frame of image data captured by the camera to generate a first enhanced image frame; (e) retrieving at least one previously captured frame of image data; (f) executing a second brightness transfer function on the at least one previously captured frame of image data to generate a second enhanced image frame, wherein the second brightness transfer function is different from the first brightness transfer function; (g) blending the first and second enhanced image frames to generate a blended enhanced image frame; repeating steps (d)-(g) so as to generate multiple blended enhanced image frames; (h) detecting, via processing of blended enhanced image frames by the processor, presence of an object in the field of view of the camera; and (i) generating an output responsive to detection of the object present in the field of view of the camera.