After I fixed infinity focus, I took this image. At the first attempt,
it was soft at the top half since the lens did not focus to infinity.
The fix was easy, just take out its bevel, unscrew three screws on
the bottom of the lens inside, then rotate the lens to attain infinity.
After tighten the screws, put the bevel back to the original place.

These screws > http://www.pbase.com/kkawakami/image/156473462