An image sensor includes an analog-to-digital conversion circuit that receives pixel signals from column lines, respectively, and converts the pixel signals into first pixel values, respectively. Data buffer clusters correspond to enable signals transferred from a timing controller, respectively, and output second pixel values. Each of the data buffer clusters stores first pixel values, which correspond to some column lines consecutively arranged among the column lines, among the first pixel values and output stored pixel values as some second pixel values among the second pixel values in response to a corresponding enable signal. A digital processing circuit performs digital processing on the second pixel values output from the data buffer clusters.