1. A method of operating an array of pixel sensor cells comprising: exposing an entirety of an array of pixel sensor cells, wherein each of said pixel sensor cells contains a light conversion unit and a floating drain; simultaneously transferring electrical charges from said light conversion unit to said floating drain in each of said array of pixel sensor cells; sensing said electrical charges in said floating drains one row at a time and for each row in said array to generate raw pixel values for each pixel sensor cell; measuring pixel values for dark pixels and generating wait-time-dependent background signal values for said array of pixel sensor cells, wherein said wait-time-dependent background signal values are dependent on a row read wait time for each row; and generating a set of noise-compensated pixel values by subtracting a corresponding wait-time-dependent background signal value from each of said raw pixel values.