An image sensor includes a pixel array including a plurality of unit pixels arranged along a plurality of rows and a plurality of columns. Each of the unit pixels includes a photoelectric conversion element generating and accumulating photocharges, a charge detection node receiving the photocharges accumulated in the photoelectric conversion element, a readout circuit converting the photocharges accumulated in and output from the charge detection node into an electrical pixel signal, the readout circuit outputting the electrical pixel signal, a capacitive element, and a switching element controlling connection between the charge detection node and the capacitive element. Each of the rows of the pixel array includes first pixels connected to a first conversion gain control line and second pixels connected to a second conversion gain control line.