Some embodiments include system and methods to obtain information for adjusting variations in features formed on a substrate of a semiconductor device. Such methods can include determining a first pupil in an illumination system used to form a first feature, and determining a second pupil used to form a second feature. The methods can also include determining a pupil portion belonging to only one of the pupils, and generating a modified pupil portion from the pupil portion. Information associated with the modified pupil portion can be obtained for controlling a portion of a projection lens assembly of an illumination system. Other embodiments are described.