Originally posted by axl Isn't DA* 16-50 coming out now??
Maybe a contender here? It's not in stock yet, and it's bit pricy, but it's longer then 16-45 and should have better IQ
I expect the 16-50 to have a comparable IQ to the 16-45, with better performance in regards to the CA problems the 16-45 exhibits. You have to understand that the DA* bonus you get is the weather sealing and SDM. Don't get me wrong tho, the IQ (CA excluded) of the 16-45 is very, very good, at least in my own experience (I own the lens). Sample images on my blog (link below).
I cannot judge the 17-70 because I have not used it. The Sigma quality control combined with the not-constant diaphragm wide open would make me reconsider the lens tho (I don't know how the lens performs wide open, but the Pentax at least is very usable at F4, and tops already at F5.6 (!!! one stop). I do think that these lenses are not really in the same league (focal-length wise). They serve different needs. I got the 16-45 because I figured I used my kit lens on the wide-end alot and was NOT liking the results
Also, since I just got my flash, I can't say the F4 is a real problem. So if you learn how to flash in a proper way, you could go for either way. Basically, it's down to your needs, then decide which one you want to get.