A method of optimizing an illumination pupil shape for a lithographic process comprises identifying a target pattern to be imaged by said lithographic process. It further comprises identifying at least one optimization point in said target pattern and identifying at least one design for manufacturing metric per optimization point. Additionally, it comprises selecting a set of illumination source points based on the identified at least one design for manufacturing metric and determining the illumination pupil shape based on the selected set of illumination source points.