Originally posted by mgoblue Clearly better than the kit in all ways except chromatic abberation which can pop up sometimes but is easy to fix. My only niggle is inconsistent focusing on the K50. It usually hits but it also has some wild misses that I don't see with my Pentax lenses.
Interesting, in my own testing the Tamron was the most reliable in terms of percentage of sharp focus hits, except for one day when I couldn't get anything from it and had to focus it manually. The the next day it was fine again. If you can do without the weather and dust seals and the long end it might work for you, but I'd also look at the Sigma 17-50, which may or may not be even better. Without a hands on evaluation, I'd go with which ever one is cheapest.
Right now the Sigma is on sale at B&H for $250 off, and is $419. You could pay more for a used one.
Looks like the best deal out there at the moment.
But unless you need ƒ2.8 for indoor or low light, the 18-135 or 16-85 are very close in IQ over that range, and offer much more useful ranges.