Using the EOS 7D and EF 70-200 f/2.8L IS II, I set the lens to the closest focusing distance and aimed at the star at the top of my yet to be completely decorated Christmas tree. After trying out various settings I decided that f/5.6 gave me a nice blurred subject and ISO 800 enabled a hand holdable shutter speed of 1/60 of a second given the image stabilization on this lens.
|200mm, f/5.6, 1/60 sec., ISO 800|
And here is what the star looks like in sharp focus:
|200mm, f/8, 1/30 sec., ISO 800|