A method and device are described for controlling and/or attenuating aiming laser beam brightness in a hand held radiometer. The beam from the laser is directed at a target measurement surface and a transversely movable element member is interposed between the laser and the target to change the beam brightness on the target. In a preferred device a slidable or rotatable element intercepts the beam between the laser and target and a calibrated opening in the element of selected size and/or shape allows part of the beam to pass through the element to provide a safe brightness at the target.