Brief Review: Tamron 28-300mm F/3.5-6.3 Di VC PZD
It's terrible. Don't buy it.
I just spent a week shooting almost exclusively with my copy of the Tamron 28-300mm F/3.5-6.3 Di VC PZD lens on a Nikon DSLR. This was the most experience I've had, by far, with the lens.
It's terrible. Autofocus is laughably inaccurate and inconsistent. The lens can occasionally produce a relatively sharp image, but that's not the norm.
Autofocusing on a subject at infinity typically produced a horrifically out-of-focus image. I got the most consistent performance by dialing in a calibration of "+17" on my Nikon D850, but even then the lens failed to focus consistently (and this definitely traded off some close-focus accuracy in favor of better landscape-distance performance).
And you cannot simply focus the lens at infinity and leave it! The distances displayed in the focus window do not seem to correspond to anything in particular. When actually focused on distant landscape objects, the lens claimed it was focused at anywhere between 50 and 200 feet.
I am getting rid of this lens as soon as I get home. I've already ordered a copy of the Nikon 28-300 f/3.5-5.6.