Originally posted by -spam- It is an EX lens afterall, so it should be in with the best of what sigma has to offer.
That means so little. Yes, it is a good lens, and it is cheap, but its rather warm by default, not as critical with digital as it was with film, but i lost many a roll of Astia to it before I ditched the brand altogether and my results went way up.
The last thing, I have never had any luck with Sigmas customer service area, so when three seperate lenses broke from them, at three different times, twice they tried to charge me for repairing lenses less than 3 months old, and even then they came back broken. The third was replaced, albeit with a bad copy of the same lens.
The Tamrons a better bet, but my real advice is to try to stick with Pentax glass. Its much much better, even the 28-70 F/4. And honestly, if you want better DoF, get wider and closer, or use a prime. With digital, F/4 is not as big of a loss as it was with film. I'd still say stick to primes as much as you can though.