Tamron has made an impressive and very capable telephoto zoom with the 100-400mm f/4.5-6.3 Di VC USD. Its size, build quality and performance suggests it will be more of a hit with amateurs and aspiring enthusiasts using APS-C DSLRs than with full-frame DSLR users.
Fast and quiet autofocus performance; Convenient size and weight for a lens of its pedigree; Effective Vibration Compensation (VC) system; Moisture-resistant construction
Tripod collar adds £109 to cost of lens; Produces heavy vignetting used with full-frame DSLRs; More expensive than its closest Sigma rival; Lens hood isn't complimentary to pull zooming