I just bought a Canon 100mm 2.8 macro USM lens and I noticed that when you focus it manually that when you reach the "limit" it keeps turning even though it's focused to its max. You can keep spinning it around and around. I didn't think this was supposed to do that since my two other lenses stop and you can't turn them any further. Is this normal? If not I am on my way back to the area I got it tomorrow and I would really love to know so I can exchange it. It really is a sick lens. Thanks!!