Embodiments of the invention provide pixel cells that allow both automatic light control and correlated double sampling operations. The pixel cell includes first and second photo-conversion devices that can be separately read out. For example, the second photo-conversion device can be the pixel cells' floating diffusion region, with an area and doping profile suitable for photo-conversion. An image sensor may include an array of pixel cells, some or all of which have two photo-conversion devices, and peripheral circuitry for reading out signals from the pixel cells. The image sensor's readout circuitry may monitor charge generated by the second photo-conversion devices to determine when to read out signals from the first photo-conversion devices.