An image sensor and an image sensing method are provided. The image sensor includes a semiconductor substrate; a photoelectric converter comprising a bias unit, which comprises a first electrode and a second electrode, and an organic photoelectric conversion layer, which selectively absorbs light and converts the light into electrons; a via contacting the second electrode to connect the photoelectric converter with the semiconductor substrate; a storage node configured to store electrons; a read-out unit to converts charge transferred from the storage node into an image signal; a pixel array comprising a plurality of pixels, each of which comprises an intermediate insulating layer; and an output circuit configured to read out the image signal from the pixel array. The quantity of light received by the organic photoelectric conversion layer is adjusted by a bias change of the bias unit.