In the second image, look at the white seat at the back. Look at the detail resolved. It's sharp.
What you are lacking is contrast - which I can only assume is mostly the UV filter's fault.
Also - the old Sunny 16 rule was: In sunlight, you should be able to shoot at F16, 125s, on ISO 100 film. This rule carries over to our dslrs pretty well - so your settings seem like you are getting half the light. Maybe it's not really that sunny when you took the shot (cloud cover, etc).
The Tamron performs well at F5.6 also, and your k-5 should also perfect very well at ISO 200. Those two settings can easily bring your shutter speed to 1/500s in comparison to your stated settings, That would instantly eliminate any fear of camera shake, even at 75mm.
Last edited by JinDesu; 05-20-2013 at 12:48 PM.