The output uniformity of a display device, such as a self light emitting display device, is improved by detecting the emitted brightness of pixels of the display device using an external detection system, controlling the pixel intensity to determine the non-uniformity of the driver circuits connected with the pixels, and generating a calibration factor for the pixels to modify the output of the driver circuits. Calibration can be performed for each pixel, or each group of pixels, such as each row and column of pixels.