An apparatus and method for use in generating calibration parameters for a printing apparatus comprising a plurality of print modules are disclosed. The method comprises printing a first plurality of test patches for each print module of the plurality of print modules, analysing the first plurality of test patches to identify at least two clusters of print modules, wherein each cluster comprises a sub-group of print modules having substantially similar performance, printing a second plurality of test patches comprising an extended calibration test patch set for each cluster of print modules, the second plurality of test patches being distributed across the print modules of the cluster, and analysing extended calibration test patch set for each cluster to determine a calibration parameter for the printing apparatus.