Primary Beam Resolution = / D

Adjacent Beams cross at H = D /

H = D / = D² /

Above H wavefront fluctuations induced are common to antennas

Interferometer "images" objects further than far-field distance H

Structures lower than H are in "near field" and not common to antennas

Near field distortions of wavefront may be "self-calibratable" if they separate into antenna-based gain errors