I recently bought a used Tamron 17-50 f/2.8 non-VC for times when I want to carry my SL1 rather than the 5DIII. I have been quite happy with the IQ. Speed of focus has been adequate and accuracy very good. Minimum focus distance is also good. Probably an economical way to get to f/ 2.8 and still have some versatility of focal length.