Methods and apparatus for imaging spectral lines are disclosed. Spectral lines are imaged using an imager that includes photosensitive cells. The photosensitive cells are arranged to form channels including banks of photosensitive cells. Horizontal blooming barriers and drains are coupled to one or more of the banks to limit accumulated charge in the banks such that the amount of charge accumulated and retained in at least one subsequent bank is incrementally increased. Charge is accumulated for spectral lines that are received by the channels to image those spectral lines.