1. An apparatus comprising: an electrostatic marking device configured to form markings on a media sheet; a readable and writable storage storing a set of control halftone dot representations; at least one density sensor configured to measure a density of markings generated by the electrostatic marking device; and a processor configured to update the set of control halftone dot representations in the readable and writable storage based on measurements by the at least one density sensor of markings made by the electrostatic marking device using halftone dots selected from the set of control halftone dot representations, the processor further configured to adjust at least one of (i) a raster output scanning power, (ii) a development field (V em ), and (iii) a cleaning field (V mc ) of the electrostatic marking device based on measurements by the at least one density sensor of markings made by the electrostatic marking device using halftone dots selected from the set of control halftone dot representations.