1. A method of processing an extended depth-of-field (EDOF) image of an iris at an imaging wavelength λ IM , comprising: capturing a raw image of the iris, wherein the raw image has a reduced modulation transfer function (MTF) based on an optical system having an amount of spherical aberration (SA) of 0.2λ IM ≦SA≦2λ IM ; normalizing the raw image; performing an MTF enhancement of the normalized raw image in polar coordinates to generate a MTF enhanced image; and generating an iris code from the MTF enhanced image.