1. An image sensor comprising: a photo sensitive device (PSD) configured to generate photocharges; a storage node configured to store photocharges generated by the PSD; a transfer switch connected between the PSD and the storage node, the transfer switch configured to control transfer of the photocharges generated by the PSD to the storage node in response to a transfer control signal; and a noise removing circuit connected to the PSD, the noise removing circuit configured to generate and store a noise signal by detecting an amount of the photocharges generated by the PSD during an inactive period, and configured to remove photocharge corresponding to a noise component from among the photocharges generated in the PSD during an active period based on the noise signal, the inactive period being a period during which the transfer switch does not transfer photocharges from the PSD, the active period being a period during which the transfer switch transfers photocharges from the PSD.