A characterization device, system, and method for characterizing reflective elements from the light beams reflected in it. The device has two variable-gain detectors on a common structure, which can be portable or fixed, and for capturing light beams reflected by a reflective element, and from at least one processor characterizing the quality of the reflected light beams and evaluating the quality of the reflective element from its reflective capacity. Each detector has a lens for increasing the signal-to-noise ratio of the reflected beam or beams, a light sensor on which the beam or beams captured by the lens are focused, an automatic gain selection system associated with the optical sensor, and a data communication device associated with the device itself. A characterization system and a characterization method for characterizing reflective elements from the quality of the light beams reflected in at least one reflective element or heliostat.