A luminaire is provided for use in determining an orientation of a camera based on an image of the luminaire captured by the camera. The luminaire comprises a light source having an on state in which it emits light and an off state in which it does not emit light, and being of a shape having a symmetry in the off state. The luminaire also comprises a controller configured to control the light source to emit said light in the on state with a lighting effect that breaks said symmetry. A device comprising receives an image of the light source from a camera, and determines an orientation of the camera relative to the light source by performing a geometric perspective calculation based on the image of the light source. An ambiguity in the orientation is resolved by detecting the asymmetry in the light emitted by the light source.