Abstract: In an embodiment an apparatus includes a scanning photographic sensor configured to acquire an image, according to an integration time of the sensor, of a scene illuminated with periodically emitted light pulses by a source, so that the image has a regular succession of bands with different luminosities when the integration time of the sensor is different from a period of the light pulses, a processor configured to generate a signature vector representative of the regular succession of bands with different luminosities being present in the image acquired by the photographic sensor, wherein the signature vector is independent of a reflectance of an objects of the scene and of a level of light in the scene, determine a frequency of the bands in the image on basis of the generated signature vector and determine the period of the pulses of the source on basis of the determined frequency of the bands in the image, and a controller configured to adjust the integration time of the photographic sensor so that the int