A method for decreasing sensitivity to errors in an imaging apparatus includes, defining an ideal pattern of dot locations as a rectilinear grid formed by an intersection of a plurality of rasters and a plurality of vertical columns; for each raster of the plurality of rasters defining a plurality of groups of dot locations; and for each raster of the plurality of rasters, vertically shifting some groups of the plurality of groups of dot locations while not vertically shifting a remainder of groups of the plurality of groups of dot locations so as to define a non-ideal vertically shifted pattern of dot locations.