Originally posted by paulelescoces
Love the 50-135 but I hear that the 16-50 is not quite of the same level, I have not had any technical issues (SDM etc..) with the 50-135 but unsure to take a risk with the 16-50...
Would like a lowlight monster.. with AF to replace the K50
... the 31 and 77 could be a good but is $$$, expecially the 31 (could fo 43 & 77 for less $$).
What do you typically use for the wider end (DA21/15?)... if I went FA Ltd I would likely still use the kit zoom to cover down to 18mm.?
I quoted this part because I think you hit on the Pentax wide angle lens conundrum in this paragraph. Currently with the Pentax lineup you kind of have to choose between a lens that is a "low light monster" and a good true wide angle. Absent some options from Sigma, I don't believe there are any options for Pentax at this time that are both wider than 30 mm and faster than f/2.8.
On a side note: Has anybody tried the Sigma 20 f/1.8? This lens has always intrigued me.
I bring this up because I think the DA*16-50 is actually a very good lens, but it really shines when you use it stopped down to f/4 or higher. The FA31 on the other hand is great at f/1.8, but it would really be nice for my shooting preferences if it were a little wider. In fact, when I say it would be really nice, I mean it would be about perfect.
The good news is that as a compliment to the DA*50-135, I think either lens would work well. It really just depends on what photos you're looking to take with the wide option.
In answer to your last question, when I owned the DA16-45 and the FA31 at the same time, I still found the DA16-45 useful in some situations, so yes I still think you would use your kit zoom. If you're looking for a way to replace your kit zoom entirely I'd suggest the DA*16-50 or either the DA21 or 15. Note: for the price of the FA31 you could instead buy both a DA15 or DA21 as well as a FA43. Something to consider.