as previously explained however a purely and truly random decision is not necessary as the plural masks preferably are colorimetrically equivalent it does not matter to output color again assuming perfect components which mask is chosen at any given pixel an example appears as fig5 where there are two versions of mask 1 u2014 i e the mask s for level 1 u2014 and also two versions of mask 2 corresponding analogously to level 2 now it is possible to randomly select one mask from among the two or more equivalent ones for each input 24 by 24 pixel by such random selection between mask 2 a and 2 b it is possible to randomly change both 1 which nozzle is used to print a given 48 by 24 dot per millimeter pixel pass 1 versus pass 2 and 2 the 24 by 24 subpixel location either the first or the second 48 by 24 dot per millimeter pixel fig4 compares the shingle mask pattern actually stamped out across the page for the conventional approach as compared with randomizing between two equivalent masks the repeating patterns that give rise to problems such as shown in fig1 and 2 are clearly visible in fig6 for the upper table for the standard approach but no such patterns appear in the lower table for the randomized approach a simulation was conducted with a software simulator known as a virtual printer the simulation used scan axis directionality errors i e nozzles firing too far to left or right with a uniform field of one drop per pixel in the coarse grid this simulation was the source of fig2 and 3 in this document those illustrations show more graphically than fig6 the reduction of banding that occurs when shingle mask patterns are broken up.