The 50mm/1.5 is a great lens and is very sharp. The focal length is very versatile but it depends on what kind of photography you are doing. The lens in question is rather big and if you do not mind having part of the view-finder being blocked by it, there is one available from Terence here in RFF. Alternatively, the Ultron is very good and fast lens, I am almost using it exclusively nowadays and you could give it a thought as its Bokeh is rather pleasant.