The lens is excellent on the 5 D III but very heavy - app. 1, 1 kgs. Just for fun I have adapted it with my FotodioX adapter on the M 240 and made only one single photo with it - this was absolutely OK. I will send this example to the forum. It is made with wide open aperture = f 4.0 because otherwise I had to shut down aperture with the Canon camera before. It is not possible to do this with the M 240 and the adapter. Vignetting will be lower when aperture set down by one or two steps. Focal length 11mm