1. A method for determining a combined motion estimate between digital images captured at different capture times, comprising: using an electronic image capture device to capture at least two digital images of a scene at different capture times; designating one of the digital images as a reference digital image, and the rest of the digital images to be non-reference digital images; designating a plurality of image regions within the digital images, wherein each image region includes at least a subset of image pixels in the digital images; determining a motion estimate for each image region by: shifting the image regions within the non-reference digital images according to each of a plurality of spatial offsets relative to the image region within the reference digital image to determine a plurality of shifted image regions, wherein the spatial offsets include horizontal and vertical offset values, each of which correspond to an integer number of image pixels; using a data processor to compute merit function values for each of the spatial offsets, wherein the merit function values are an indication of an amount of difference between the image region in the reference digital image and the shifted image regions in the non-reference digital images; using a data processor to fit a fitting function having a predefined functional form to at least a subset of the computed merit function values, wherein the fitting function provides an estimated merit function value as a function of spatial offset; and determining the motion estimate responsive to the fitting function; determining the combined motion estimate by combining the motion estimates for the plurality of image regions, wherein the combined motion estimate is determined by forming a weighted combination of the motion estimates for the plurality of image regions, each motion estimate being weighted with a weighting coefficient, and wherein the weighting coefficient for each image region is determined responsive to the shape of the corresponding fitting function; and storing an indication of the combined motion estimate in a processor-accessible memory.