To this stage a large amount of information has accumulated on one‐dimensional broadband frequency channel characteristics of the visual system. Only recently have attempts been made to define additional two‐dimensional narrow‐band response profiles‐particularly in central vision. In this paper questions concerning the number, tuning widths and phase sensitivity of such two‐dimensional narrow‐band coding units are reviewed. Results with grating and two‐dimensional images are discussed, particularly within the context of energy processing and information reduction strategies which reflect human performance. Finally, a consequent principle of univariance is defined and shown to hold with such