I bought a new 5D mark II and 16-35 L II lens. I was doing test shooting inside my room with my new toys using wide angle lens and with 24-70L which I already own. Both has the same aperture of f2.8 and AF was working fine with 16-35 L-II in available light but when I tested using 24-70 L AF was searching on. I am not surprised about 5D Mark II is not equipped for low light coz I got ample info abt 5D M-II's Auto Focus with the earlier post. Still I made my mind to go for it just bcoz it's a affordable full frame camera by Canon. I am just trying to understand the concept. I appreciate all, for your comments in advance Thanx..