Backprojection-based reconstruction and correction for distance-dependent defocus in cryoelectron microscopy

We study two methods of micrograph processing in cryo- electron microscopy: the defocus-gradient corrected back- projection algorithm and the correction of micrographs for the contrast transfer function based on the frequency-distance relation. Analyzing integral images produced by the methods we conclude that they are asymptotically equivalent within the framework of stationary phase approximation.