Comments about Tamron Tamron 10 - 24mm f/3.5-4.5 DI-II B.I.M. (Built-in Motor) LD Aspherical (IF) AF Wide Zoom Lens, for Pentax Digital SLR Cameras - U.S.A. Warranty:

After research, I purchased this lens instead of the equivalent Pentax ultra-wide zoom. I use it for creative HDRI effects while shooting landscapes and buildings.

The bokeh is very decent, and center resolution is very good at all focal lengths. Edge resolution is acceptable when stopped down. The barrel distortion is considerable throughout. Chromatic aberration is highest at 10mm, but this is pretty easy to fix in post processing.

This lens is a fine ultra wide choice for casual shooting and a lot less money than the native Pentax equivalent.