A method for operating an image sensor including at least one pixel, wherein a first integration section is a charge integration section for a light having a middle intensity of illumination or a low intensity of illumination, and a second integration section is a charge integration section for a light having a high intensity of illumination, and wherein the first integration section is longer than the second integration section, the method comprising: draining and erasing charges of a charge conversion unit and a charge storage unit; starting charge integration of the second integration section in the charge conversion unit; transferring (a) charges integrated in the charge conversion unit during the second integration section to the charge storage unit by a transfer switching unit; reading out (b) a signal level of charge integrated during the second integration section at a same time of transferring (b) the charges; draining (c) the charges of the charge storage unit after reading out the signal level in the second integration section, wherein a reset switching unit is operated while the transfer switching unit is turned on, transferring charges integrated during the first integration section following the second integration section in the charge conversion unit to the charge storage unit by the transfer switching unit, wherein the reset switching unit is operated again while the charges are integrated in the first integration section to drain (d) the charges of the charge storage unit; reading out (e) a signal level for charge integrated during the first integration section after the charges integrated in the charge conversion unit during the first integration section are transferred to the charge storage unit; and calculating a light intensity by using the signal levels of the first and second integration sections, wherein the signal level of the second integration section is readout based on the quantity of charges stored in the charge conversion unit, the transfer switching unit and the charge storage unit of the image sensor, and wherein the operation for reading out the signal level in the second integration section for the light having the high intensity of illumination is performed simultaneously with an operation timing of the transfer switching unit. draining and erasing charges of a charge conversion unit and a charge storage unit; starting charge integration of the second integration section in the charge conversion unit; transferring (a) charges integrated in the charge conversion unit during the second integration section to the charge storage unit by a transfer switching unit; reading out (b) a signal level of charge integrated during the second integration section at a same time of transferring (b) the charges; draining (c) the charges of the charge storage unit after reading out the signal level in the second integration section, wherein a reset switching unit is operated while the transfer switching unit is turned on, transferring charges integrated during the first integration section following the second integration section in the charge conversion unit to the charge storage unit by the transfer switching unit, wherein the reset switching unit is operated again while the charges are integrated in the first integration section to drain (d) the charges of the charge storage unit; reading out (e) a signal level for charge integrated during the first integration section after the charges integrated in the charge conversion unit during the first integration section are transferred to the charge storage unit; and calculating a light intensity by using the signal levels of the first and second integration sections, wherein the signal level of the second integration section is readout based on the quantity of charges stored in the charge conversion unit, the transfer switching unit and the charge storage unit of the image sensor, and wherein the operation for reading out the signal level in the second integration section for the light having the high intensity of illumination is performed simultaneously with an operation timing of the transfer switching unit.