1. A method of optimizing a lithographic process for imaging a pattern comprising a plurality of features onto a substrate using a lithographic apparatus, the lithographic apparatus having a controllable illumination system arranged to illuminate a patterning device with radiation and a controllable projection system arranged to project an image of the patterning device onto the substrate as a patterned beam of radiation, the method comprising: selecting a feature from the plurality of features; determining an illumination setting for the illumination system to optimize imaging of the selected feature; determining a projection setting for the projection system to optimize imaging of the selected feature taking account of the illumination setting; and verifying the effect of the illumination setting and the projection setting on the image of at least a part of the pattern, the at least part of the pattern including a feature not selected in the selecting step.