A method of generating control data for nozzles of a printhead of an ink jet printer to deposit an aggregate volume of ink into target regions of a substrate, the aggregate volume for each target region to be within a predetermined volume tolerance range, each of the nozzles generating at least one respective droplet volume, the method comprising: receiving information representing statistical populations representing each respective droplet volume, the statistical populations comprising a plurality of values for each nozzle; for each of the target regions, calculating a respective combination of droplets for which means representing corresponding droplet volumes sum to a value restricted to be within the predetermined tolerance range; generating the control data in a manner correlated with each combination, the control data sufficient to instruct relative motion between the printhead and substrate to bring each of the nozzles associated with each combination into proximity with the respective target region, and to instruct firing of each of the nozzles associated with each combination to deposit each droplet volume associated with the respective combination in the respective target region, wherein the control data is sufficient to instruct relative motion between the printhead and substrate to concurrently bring at least one nozzle associated with each combination into proximity with the respective target region, and to instruct firing of the at least one nozzle associated with each combination to concurrently deposit the droplet volumes in the respective target regions; and wherein the method further comprises controlling an ink jet printing mechanism to perform the relative motion and the firing of the nozzles associated with the combination, in dependence on the control data. receiving information representing statistical populations representing each respective droplet volume, the statistical populations comprising a plurality of values for each nozzle; for each of the target regions, calculating a respective combination of droplets for which means representing corresponding droplet volumes sum to a value restricted to be within the predetermined tolerance range; generating the control data in a manner correlated with each combination, the control data sufficient to instruct relative motion between the printhead and substrate to bring each of the nozzles associated with each combination into proximity with the respective target region, and to instruct firing of each of the nozzles associated with each combination to deposit each droplet volume associated with the respective combination in the respective target region, wherein the control data is sufficient to instruct relative motion between the printhead and substrate to concurrently bring at least one nozzle associated with each combination into proximity with the respective target region, and to instruct firing of the at least one nozzle associated with each combination to concurrently deposit the droplet volumes in the respective target regions; and wherein the method further comprises controlling an ink jet printing mechanism to perform the relative motion and the firing of the nozzles associated with the combination, in dependence on the control data.