Hello. The Tamron 17-50 / 2.8 is used on a Sony 550, in addition to Sony 18-200. Application mainly interior photos and landscape photos on a moving vehicle, aperture priority most often. Results good to very good, good reactivity housing remains nervous autofocus "pedal" good. Very good value for money (The dream would be a Tamron 70-200 / 2.8 of the same value ....)