How much angle of view is needed?
The best ultra wide zoom for the buck may be the Sigma 8-16 DC, no filters possible, extreme angle of view.
The Sigma 10-20/4.5-5.6 and 10-20/3.5 are okay, but not the sharpest.
The new Pentax DA* 11-18 is the best you can get, but expensive.
The Pentax DA 15 Ltd. is very contrasty, sharp in the center, but shows brutal CAs who ruin the border sharpness.
The Pentax DA 12-24 show some moderate CAs, but is a great lens.
The Pentax DA 10-17 Fisheye is something special, not for everyday use.
Maybe you find a Pentax DA 16-45 in good condition, also not so bad if mechanically okay.
A Sigma 17-50/2.8 EX (with or without OS) may also be a suitable offer, a fine lens.
The sharpest lens of all but the new DA* is the Sigma 18-35/1.8 [Art], but with nervous bokeh.
And forget the older lenses. They are not so recommended.
Take your choice!
Last edited by Austro-Diesel; 07-05-2020 at 01:55 PM.