Another option that works well for me is using "Selet/Color Range", there you can adjust the fuzziness of the selection manually. If there are still artifacts, I hit the quick mask button at the bottom of the tool panel, zoom in, brush out what I don't want with a NEG(black brush), click back on the Quickmask button and voila, the selection is precise.

___
Ockham's razor- It's that simple