The subject disclosure is directed towards controlling the intensity of illumination of a scene or part of a scene, including to conserve illumination power. Quality of depth data in stereo images may be measured with different illumination states; environmental conditions, such as ambient light, natural texture may affect the quality. The illumination intensity may be controllably varied to obtain sufficient quality while conserving power. The control may be directed to one or more regions of interest corresponding to an entire scene or part of a scene.