Should you buy Tamron Lens AF 200-400mm f/5.6 or NOT? - YouTube
Amazon.com : Tamron AF 200-500mm f/5.0-6.3 Di LD SP FEC (IF) Lens for Canon Digital SLR Cameras (Model A08E) (Discontinued by Manufacturer) : Camera Lenses : Electronics
Tamron AF 200-500mm f/5-6.3 SP Di LD IF - Review / Lab Test Report