If you can afford it the Summicron is the one to get. If not and if you are to choose one of the Elmar 50mm 2.8, get one from the late 60s early 70s. They perform equally good if not better than the late elmars, they are better made, but you have to make sure you get one without haze and spots on the coatings. A point to note with the older elmars is that changing the aperture with the focusing released from infinity turns the barrel.