An image sensor includes a pixel array including a plurality of pixels; a ramp signal generator configured to generate a ramp signal; a plurality of first attenuators with each first attenuator connected to a respective column of the plurality of pixels, and each first attenuator configured to receive a pixel signal from a respective pixel belonging to a selected row; a plurality of second attenuators with each second attenuator corresponding to a respective column, and each second attenuator configured to receive the ramp signal from the ramp signal generator; and a plurality of analog-to-digital converters configured to output digital signals by comparing first signals output from the plurality of first attenuators and second signals output from the plurality of second attenuators, in which each of the plurality of first attenuators and each of the plurality of second attenuators comprises a first capacitor and a second capacitor.