An image sensor, including a pixel array including a first unit pixel including first a plurality of photodiodes and a second unit pixel including a second plurality of diodes; a readout circuit configured to: obtain a reset signal from the first unit pixel and the second unit pixel, obtain a first single pixel signal from a first photodiode of the first unit pixel, and a second single pixel signal from a second photodiode of the second unit pixel, and obtain a first summed pixel signal from the first unit pixel, and a second summed pixel signal from the second unit pixel, wherein the first photodiode is disposed in position with respect to the first unit pixel which is different from a position of the second photodiode with respect to the second unit pixel.