Techniques for automatic exposure correction of images are provided. In particular, the exposure of an input image may be improved by automatically modifying a non-linear function that characterizes the luminance of shadow, mid-tone, and highlight portions of the image. The input image may be segmented into a number of regions and each region is assigned a zone, where the zone indicates a specified range of luminance values. An initial zone assigned to a region of the image may be changed in order to reflect an optimal zone of the region. Based, in part, on the optimal zones for each region of the image, luminance modification parameters may be calculated and applied to the non-linear function in order to produce a modified version of the input image that improves the appearance of overexposed and/or underexposed regions of the input image.