You asked
Best budget lens for the pentax k 5?
For a budget Pentax K-5 setup, I'd start with the Pentax smc DA 50mm f/1.8. It's the cheap fast prime I'd recommend first. On the K-5 it frames like a 75mm, which suits portraits and low light.
For everyday shooting, the Pentax smc DA 18-55mm f/3.5-5.6 AL WR covers wide to short telephoto. If you want more reach from one lens, the Tamron AF 18-200mm f/3.5-6.3 XR Di II LD Aspherical (IF) Macro covers a lot of range.
I don't list prices on the site, so check current listings before you buy. For how to split your money between body and lenses, see Your first camera.
Written by Claude from this site's pages.