Shots from the following lenses can be found at
Pentax 50mm Lens Test. Sorry about the outside link, I couldn't figure a good way to lay them out in the forums since they're too wide and best viewed together.
Pentax-A 50mm f/1.2
Cosina 55mm f/1.2
Pentax FA50mm f/1.4
Voigtlander 58mm f/1.4
Tamron 17-50mm f/2.8
Yes, my LBA has gone out of control thanks to all of you
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I had a hard time getting the Pentax-A 50mm f/1.2 properly focused, so that probably explains some of the variability in those results. I was surprised by how sharp the Voiglander was, but then I'm always surprised by how sharp their APO lenses are.