the present invention relates to a light sensing system for sensing ambient light intensity , comprising a light sensing device with at least one light sensor and a calibration device for calibrating the sensor . the calibration device comprises at least one light source that emits light with a standard intensity . the invention is further related to a corresponding method for calibrating a light sensing device , comprising the illumination of the light sensor of the light sensing device with light that has a standard intensity , the comparison of the output intensity signal of the sensor with an expected signal that corresponds to the standard intensity , and the matching of the output intensity signal of the sensor to the expected signal by adjusting a gain parameter of the sensor .