Disclosed herein are cameras and image sensors, and electronic devices containing them, having pixel arrays operable both for obtaining images and detecting flicker in ambient light. For flicker detection, such as prior to image capture, light-generated current from a set of pixels of the pixel array is received at a transimpedance amplifier (TIA) that is formed in a common semiconductor substrate with the pixel array. An output signal of the TIA is digitized and signal processed to detect the flicker in the ambient light. Also disclosed are image sensors having pixel arrays with an embedded modulated light source. The modulated light source may be used for proximity detection, either by time-of-flight or intensity variation of reflected light.