1. An automatic exposure control circuit, comprising: a hierarchical histogram generator for generating a plurality of histograms of differing resolutions, each histogram comprising at least one bin, each bin representing a number of pixels in an image having a pixel value within a respective unique range of pixel values, each histogram also corresponding to a unique range of pixel values; and an image exposure adjustment module for adjusting an image exposure setting according to a distribution of pixel values determined from the plurality of histograms.