Hey all, I'm going to a wetlands bay to shoot birds, eagles etc... I was going to rent a super telephoto lens (400MM 2.8) as well for my buddies Cannon 7D.

I've never used a lens this large and was wondering if anyone had tips they could kindly offer. The conditions should be amazing.. snowy/ice backgrnd and clear blue skys in the upper 40's.

What settings should I be most concerned about, also wondering how the video might work on lens that large.

These are the lens I am looking at renting