1. A method of controlling a print engine, the method comprising: printing a first test image including a number of scans of printing components at a first setting of the array of printing components; printing at least a second test image by a number of scans of the printing components at a modified setting of the array of printing components, the modified setting being different from the first setting, wherein the modified setting provides a modified setting for each one of the printing components which is varied according to the position of the respective printing component in the array; optically scanning the printed test images and determining the distinctiveness of a scan band within the printed test images for each one of the test images; and deriving an optimum setting of the array of printing components from a comparison of the determined distinctiveness; wherein determining the distinctiveness of a scan band within the printed test images comprises: optically scanning each test image, and for each test image, determining an amplitude of the test image at a scan band frequency, and wherein deriving an optimum setting of the array of printing components comprises comparing the determined amplitudes of the test images and selecting a setting which resulted in an test image having a low amplitude when compared to other test images.