I own a Canon 5D Mark II and am looking for a Fast 50mm Lens I can use wide open. Unfortunately, it seems that all the f/1.0, 1.2, 1.4 and 1.8 lenses are not very sharp at their widest aperture. Can anyone suggest a lens between 40mm and 70mm focal length that is really fast, i.e. : f/1.0 to f1.4. I need the widest aperture to produce sharp results. I don' care if the manufacturer is not Canon or if I have to use a lens adapter.