I just bought a canon 50 L lens and was checking it over this evening; I shook it lightly, and it rattled a little bit. I also have to micro adjust the focus on it on my 5D Mk III 15 points!! Never had to do it that much with any of my other lenses! On my 1dx I have to adjust it the same direction 5 points. Should I return the lens? Or send it to Canon? Or just live with it? I need some advice from someone with a little more experience.