The invention relates to a method and device for determining object property of an object with the aid of images that have been recorded with the aid of a camera. Further, the invention relates to a method for determining a calibration parameter for a stereo camera. For determining the object property of an object, the object is defined in a first image recorded with the aid of the camera. Further, the brightness of a defined object is determined. Each time after a preset time interval, a further image is recorded with the aid of the camera. The object is defined in each of the further images and each time, the brightness of the defined object of each image is determined. Dependent on the brightness curve, an object property is assigned to the object.