An image sensor includes a pixel array including pixels, wherein each pixel includes at least one photodiode generating electrical charge and a pixel circuit providing a pixel signal based on the electrical charge. The images sensor also includes a logic circuit configured to generate an image based on the pixel signal, wherein the pixel circuit includes a parallel-connected first reset transistor and second reset transistor, and the logic circuit determines whether the second reset transistor is turned ON/OFF based on a level of incident light received by the at least one photodiode during an exposure time period.