An organic light emitting diode (OLED) display, including a pixel portion having a plurality of pixels connected to scan lines and data lines, a scan driver adapted to generate and supply scan signals to the scan lines, a data driver adapted to generate and supply data signals to the data lines, an optical sensor adapted to generate an optical sensing signal according to an intensity of light, and a data converter adapted to store input image data or changed data from the input image data corresponding with the optical sensing signal. The data driver may be adapted to generate the data signal corresponding to the input image data or the changed data.