A method for operating an image display apparatus, comprising: receiving a three-dimensional, 3D, image, wherein the 3D image includes a left-eye image and a right-eye image; calculating an Average Picture Level, APL, of the 3D image, the APL representing average luminance of the 3D image frame; changing a depth of the 3D image according to the calculated APL, wherein the depth of the 3D image corresponds to a disparity between the left-eye image and the right-eye image of the 3D image; and changing a luminance of a current frame of the 3D image having the changed depth according to a luminance difference between the current frame and the previous frame of the 3D image having the changed depth when the calculated APL is equal to or lower than a first threshold or equal to or higher than a second threshold larger than the first threshold as a result of degraded crosstalk characteristics caused by inappropriate overdriving, wherein the depth changing comprises decreasing the depth of the 3D image, when the calculated APLs of the left-eye image and the right-eye image are equal to or lower than the first threshold or equal to or higher than the second threshold larger than the first threshold as a result of degraded crosstalk characteristics caused by inappropriate overdriving, wherein the depth changing comprises maintaining the depth of the 3D image without any change, when the calculated APLs of the left-eye image and the right-eye image are higher than the first threshold and lower than the second threshold, and wherein the luminance changing comprises changing the luminance of the current frame according to the luminance difference between the current frame and the previous frame, referring to an overdriving data look-up table having luminance data. receiving a three-dimensional, 3D, image, wherein the 3D image includes a left-eye image and a right-eye image; calculating an Average Picture Level, APL, of the 3D image, the APL representing average luminance of the 3D image frame; changing a depth of the 3D image according to the calculated APL, wherein the depth of the 3D image corresponds to a disparity between the left-eye image and the right-eye image of the 3D image; and changing a luminance of a current frame of the 3D image having the changed depth according to a luminance difference between the current frame and the previous frame of the 3D image having the changed depth when the calculated APL is equal to or lower than a first threshold or equal to or higher than a second threshold larger than the first threshold as a result of degraded crosstalk characteristics caused by inappropriate overdriving, wherein the depth changing comprises decreasing the depth of the 3D image, when the calculated APLs of the left-eye image and the right-eye image are equal to or lower than the first threshold or equal to or higher than the second threshold larger than the first threshold as a result of degraded crosstalk characteristics caused by inappropriate overdriving, wherein the depth changing comprises maintaining the depth of the 3D image without any change, when the calculated APLs of the left-eye image and the right-eye image are higher than the first threshold and lower than the second threshold, and wherein the luminance changing comprises changing the luminance of the current frame according to the luminance difference between the current frame and the previous frame, referring to an overdriving data look-up table having luminance data.