I snagged a K-5 a couple of months ago on a whim when I noticed how low the price was and I didn't really need any of the new K-5 II updates. I bought the 18-55 WR and the Tamron 70-300 for it. I love the camera, but those lenses are mediocre at best.
I'm struggling to find a good zoom. (high sharpness, low distortion and aberrations) I'm struggling so much that Nikon and their world-class sensors are looking really good right now. Please help! I really do like the K-5! A Nikon full-frame setup would be heavy and expensive, even with the "consumer-grade" D600, so it would be nice I could find glass to make a K-5 setup work for me.
Pentax:
I thought about the 18-135 WR, (the WR is nice, and the DC focus motor is quieter than the screw drive), but it seems to really be only good around 24mm which leaves me feeling like I'm paying for a lot of lens I won't ever use. I dismissed the DA* 16-50/2.8 pretty quickly, as it seems to be pretty soft in the corners and is very expensive for a dressed-up Tokina. (Reviews database uses phrases like "besieged by chromatic aberration", so the current price of around $1500 makes the DA* absolutely out of the question.) The 17-70/4 seems OK, but the troublesome SDM-only focusing does worry me, and it's not as sharp as the Sigma 17-70.
Sigma:
Since Sigma hit a home run with that new 35/1.4 "Art" lens I thought the new 17-70 "Contemporary" might be perfect for me, but it seems to be getting mediocre reviews. The 17-50/2.8 won the comparison here but had some minor flare issues.
Tamron:
Tamron 17-50/2.8 (non-VC version) seems decently sharp to the corners @ f/8-f/11 and the prices are fantastic right now, but I've read that the AF is loud (screw drive?) and the Sigma is sharper in the corners. Is the Tamron a decent lens for landscapes? If so, the price is right, maybe is the Sigma 17-50 is the right choice. (?)
Help!
Thanks in advance.