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 photoconversion devices to determine when to read out signals from the first photoconversion devices.