A method includes obtaining multiple spatially-displaced input images of a scene based on image data captured using multiple imaging sensors. The method also includes dividing each of the input images into multiple overlapping sub-images. The method further includes generating multiple overlapping sub-image gain maps based on the sub-images. In addition, the method includes combining the sub-image gain maps to produce a final gain map identifying relative gains of the imaging sensors. An adjacent and overlapping pair of sub-image gain maps are combined by renormalizing gain values in at least one of the pair of sub-image gain maps so that average gain values in overlapping regions of the pair of sub-image gain maps are equal or substantially equal.