> How do the images from the Tamron 24-135, the Sigma 100-300 & the Tamron > 28-300 XR compare, especially for resolution/sharpness? User reviews I read > on Internet vary a lot in their opinion on the quality of the 28-300 lens > and the images it produces.
I'd be pretty suspicious as to the optical qualities of any 28-300 lens. (Call me old-fashioned, but that'd be asking too much for any zoom design to succeed with.) It sounds as if you're looking for an autofocus lens. However, if you're amenable to a ~manual~ focus 100-300, I highly recommend the Tokina AT-X 100-300/4, a superb long zoom. Fred
