My experience is that the non Achromat CFi Version of the Sonnar is an excellent lens. I borrowed it from a friend and got great results. The sharpness was there and the colour and light work very naturally on the Provia 100F. On the other hand, since I couldn`t afford this lens, I ended up with the 250mm lens that I am not satisfied with. It's the f/4 Tessar version that only works with focal plane shutter cameras. It could be that the cause of poor image quality is my tripod suffering from the kick it gets from the shutter, but if I was to compare the results I got from the Cfi Sonnar with my Tessar I would say that The Sonnar is a much better lens. A lens that I could easely live with! The Tessar could prove to be a great lens for portraits, at least that is it's reputation, but for landscape…I will see. Perhaps when I put it on a beefy tripod with a decent ballhead things will be different. As for the Achromat version, I have no experience with it apart from holding it in my hands for a few second from what I can tell that it is a little smaller and more lightweight lens than the non Achromat version. But I did read that to bring out the advantages this lens has over the non Achromat version one needs to have flawless technique and perfect conditions, otherwise it is no better than the very good and much cheaper Cfi Sonnar.