1. An imaging system comprising: a shiftable image plane generated from photons emanating from an object and passing through a lens; a detector plane positioned to receive the photons of the object that pass through the lens; and a computer programmed to: characterize the lens as a lens function; acquire two or more elemental images of the object with the image plane at different axial positions with respect to the detector plane; determine a focused distance of the object from the lens based on the lens function and the two or more elemental images acquired; and generate a depth map of the object based on the determined focused distance.