Originally posted by jatrax Considering how many lenses you have tried I suspect you have more experience than many of us. So quite hard for anyone to say what will match your expectations.
I shoot with the 16-85 on the K-3II and my wife uses the 18-135 on her K-3. Sometimes my shots are better, sometimes her's are. I believe the 16-85 is slightly sharper overall and definitely better on the edges than the 18-135 but the 18-135 has much more reach and stopped down it is very hard to see the difference.
Not sure if that helps or not. My wife is convinced her 18-135 is perfect (for her) and I am equally convinced that the 16-85 is perfect (for me). I used the DA*16-50 for many years and except for the lack of f/2.8 I find the 16-85 images comparable in good light and stopped down a bit.
Another family with the 18-135 love hat thing going. Glad to know ours isn't the only one.
Quote: I think one obvious choice is the 16-85, but I'm wondering whether the 16-85 is truly better than what I already had, it's quite pricey, even used. I also have another option to buy a Sigma 17-70 C, which cost half of the Pentax, but no WR. In term of image quality, are they comparable? Should I stay with the 20-40 and forget about zoom?
To me this is a no brainer.
You don't want lens changes, you want to get the most out of what's on your camera. Since I like the 18-135 and you don't, I'm going to say higher than average standards.
The 18-135 was built under the "lenses for the way people take pictures" philosophy. The 16-85 was built under the "modern lenses for modern sensors" philosophy.
Compared to the 17-70, need I point out, 1 important mm wider on the wide end 15 longer on the long end, WR and DC motor.
I'm not seeing a choice here. You are in a "widest focal length range n a standard zoom" category.
As for the juggling act around cost, I can't help you with that. I'd love a 16-85 for my Tess, I think she'd love it. but so far, it's not in the budget. I made a decision to get the 18-135 years ago, when it was the latest thing since sliced bread, and have a lot of use with it. I don't think I should have waited for the 16-85. The 16-85 is the new 18-135.
The only reason for passing on the 16-85 would be you can't afford it. With WR and DC, you're not competing with the value even at half the price. IN our case, we probably will own a 16-85 at some point. I'm not wasting time and money buying make do alternatives. (or course we still have our 18-135, 28-105 and Tamron 17-50. We aren't suffering in the meantime for standard type zooms.)