An image sensor comprises an upper chip including pixels; and a lower chip placed below the upper chip, wherein a pixel of the pixels includes an optical conversion element configured that light is incident on the optical conversion element, a first storage gate or a first storage node which is electrically connected to the optical conversion element and configured to store electric charge transferred from the optical conversion element during a first time interval, and a second storage gate or a second storage node which is electrically connected to the optical conversion element and configured to store the electric charge transferred from the optical conversion element during a second time interval different from the first time interval, the pixel is configured to generate a first pixel signal on the basis of the electric charge stored in the first storage gate, the lower chip includes a frame buffer.