An image sensor includes a first unit pixel including a first sub-pixel and a second sub-pixel, a second unit pixel including a third sub-pixel and a fourth sub-pixel, a timing controller configured to apply a first effective integration time to the first sub-pixel and the fourth sub-pixel, such that a first sensing signal and a fourth sensing signal are generated from the first sub-pixel and the fourth sub-pixel, respectively, and to apply a second effective integration time shorter than the first effective integration time to the second sub-pixel and the third sub-pixel, such that a second sensing signal and a third sensing signal are generated from the second sub-pixel and the third sub-pixel, respectively, and an analog-to-digital converter configured to perform an averaging operation on the first sensing signal and the fourth sensing signal or on the second sensing signal and the third sensing signal.