An image sensor, comprising a pixel region in which a plurality of pixel units are arranged, each pixel unit having first and second photoelectric conversion portions, a first output portion that outputs, outside of the image sensor, a first signal based on a signal from the first photoelectric conversion portion of the pixel units, and a second output portion that outputs a second signal based on a signal from the first photoelectric conversion portion and a signal from the second photoelectric conversion portion of the pixel units, wherein output of the first signal from the first output portion and output of the second signal from the second output portion are performed in parallel.