An image sensor includes a pixel array having a plurality of layers and a control unit. Each of the plurality of layers including pixels having a photoelectric conversion element and a transmission transistor therein. The photoelectric conversion element is configured to collect charges during an associated charge collection time period and the transmission transistor is configured to transmit the charges to a respective floating diffusion node at an end of the charge collection time period. The control unit configured to individually instruct the transmission transistors associated with different ones of the layers to transmit the charges to the respective floating diffusion nodes such that the charge collection time periods associated with the photoelectric conversion elements implemented in at least two of the layers differs in length.