Quote: After reading so many reports about Tamron 70-200 zooms being faulty, I would never recommend buying one despite the so-called optical excellence that is often reported.
After reading through the reviews on this site
< here > this lens rated 8.97 almost 9... of the 33 who rated the lens 30 were very impressed. Three people had problems serious enough to return the lens. Reading through the reviews, one of them bought the lens damaged from someone second hand, that's on whoever sold it to him not on Tamron. ANd other has issues with a sticky aperture. If you know what the issues are, use your lens right way and return it right away if you have any issues. A 10% failure rate is very high, but as it said in one of the articles, you pay 1600 for a better build quailty, or you pay $700 for this lens, and get better optics. Clearly the AF is not Canon or Nikon quality, but then, what Pentax lens is, at any price?
I still plan to get this lens eventually. But I'll return it at the drop of a hat and go for another one. After all 90% of those who have one are giving it all 9's and 10's. The other 10% the build quality is clearly an issue, but it's a manageable isue. Buy from a reputable dealer. The Henrys price is $899 but, I can return it for a full refund, no questions asked for the first 10 days, and exchange it for up to 30 days. When I bought my DA*60-250 I went exactly that route.. Sigma 120-400 (returned, defective lens), Sigma 120-400 OS (returned, poor optical quality) , DA* 60-250. I now wish I'd started with the Tamron. The lens in one of the reviews in tested on a 3500 x 2200 sensor. There's no justification in suggesting this lens won't perform on 16mp sensor. 30 of 33 Pentax forum users recommend this lens. If it's not DOA however the % is a lot better. How bad can it be?
As for the better TC performance with the Sigma TC , one of the reviewers notes that the Tamron works better on the Sigma converter than the Sigma does.
It should be noted that a 10% failure rate is high, I'm not discounting at all what bossa is saying. I just think the trick is to make sure you get a good copy of the lens, and don't buy it if you're not willing to take it back a few times if needed, and you should be good. Just on that basis alone buying it mail order might be pretty risky. You might want to deal with a bricks and mortar store. Henry's has a no questions asked return policy.. if I don't like it for any reason, I can bring it back. With my 120-400 OS they asked I said, the image quality isn't good enough at 400.. that was it.