Pentax SMC DA * 16-50mm F2.8 ED/AL (IF) SDM

This lens is excellent! Do not take into account some "technical test" which are found on the internet - this lens is built to take pictures of real world, not for some resolution tests.
As a standard zoom i offers everything. I use it mainly for landscapes, where it performes just great. Thanks to large apperture you can go for portraits as well and as it is SDM lens, some action is also no problem.
I love it is weather-proof - do not have to worry about shooting misty landscapes or even in light rain.

I have only one problem with filters (I use them a lot for landscapes). When I use a polarizer + Cokin P gradual filter on the wide end (16-17mm) shooting with the camera in vertical position there are two issues:
- light vignetting caused by Cokin filter holder (this can be easily corrected in software)
- Cokin P filter is to small when using gradual ones on the sky: If the sky is only one fifth of the frame, I have to push it down to a quarter at least - otherwise the edge of the filter is still in the frame
But this is just my issue as I use Cokin P - I will have to switch to Cokin Z or LEE filters

- Excellent image quality
- Weather-proof
- Solid bulit quality
- Large apperture
- Cheaper than competition (especially Canon L)

- A bit heavier
- If you use filters extensively, than Cokin Z or LEE is a must for 16mm

Pentax 16-45mm (also very good)
Pentax 40mm
Pentax 70mm

No experience