Originally posted by paperbag846 I really think the value of the 16-50 lies in weather sealing, SDM, quickshift, etc.
If you don't need these things, you are paying an awful lot for features you might not use.
That pretty much sums it up. While people will argue and defend their lens choice - constructively as this thread has been - it comes down to the fact that a good copy of each of the lenses (Pentax/Tamron/Sigma) will be close in image quality to the others. None is a poor choice. It comes down to personal preference. The Pentax adds $200-300 in cost for a few physical features (WR, Quick Shift, SDM). If you dont need/want them, youre probably better off with the Tamron/Sigma.
Originally posted by Frogfish Pretty much
I still haven't got my hands on the new 17-50 Sigma 2.8 yet but if I can't by the weekend then I'll buy the Tamron for now and try out the Sigma later, an easy and low cost upgrade if necessary.
I didnt look at the Sigma too closely when I was assisting my friend with this very same purchase question. The Tamron was well regarded, cheaper, had a longer warranty, and most importantly, had rounded aperture blades...which the Sigma did not. As my friend is kind of a self proclaimed bokeh freak...this made the decision a no brainer for him.