Examples include: a leveling system for a top feeder of a printer, where the top feeder includes a media positioning arrangement. The leveling system has a detector for detecting reflected light and generating a three-dimensional image comprising media positioning regions corresponding to the media positioning arrangement on a top sheet of a media stack installed into the top feeder. Also, the leveling system has an actuator configured to adjust heights of different points of the bottom of the media stack. Further, it has a controller for selecting, based on the three-dimensional image, adjustments to the heights for improving leveling of at least one of the media positioning regions; and controlling the actuator to implement the adjustments.