An image sensor includes pixels which are of the four-transistor, PIN photodiode type. In each pixel, the charge on a photodiode is transferred by a transfer gate to a sensing node. Readout of reset and read voltages is via an amplifier. A gain capacitor is connected in feedback across the amplifier. Read and reset gates are controlled so that the pixel is reset to a virtual ground voltage controlled by the gain capacitor. This is independent of the pixel parasitic capacitance.