Originally posted by Pentaxor the only downside of the Tamron is it's slow and noisy AF speed, zoom creep, built and QC issues (centering defect). getting a lemon is the last thing that you would want. it is said that the Tammy is a monster on an APS-C dslr, but not as quite as great on a full-frame but still display an excellent center sharpness. although what confuses me is that the MTF results on a FF has an outstanding score as compared to the APS-C, but the APS-C verdict is a lot higher than the FF. I dont know how photozone arrive or use and interpret these MTF results, but it seems it is inconsistent or does not reflect on the final conclusion about the lens. could anyone explain how a lens with a 3000 MTF mark on a FF gets only a 2 and a half approval, while a 2000 MTF mark on an APS-C gets a 4 approval rating. maybe photozone mixed up the MTF results?
I don't know for sure but sounds like you are talking about the Tamy 18-250.
The Tamron 28-75 F2.8 that i have is very sharp, does not have any zoom creep, just the opposite, is a pretty lightweight walk around lens despite its fast F2.8, AF is pretty good i think - it burps once or twice and is there. I bought it new recently for $400 plus. I think the price is why folks are not going for the Sigma.