Canon EF 400mm f / 5.6L USM

Advantages: Sharp throughout the frame.
For such money, nothing like the competitors simply do not have.
Size and weight for 400 mm.
Fast focus and accurate, with a convenient ring that can be twisted constantly like in all expensive lenses.
Well-thought-out ergonomics, for example with a folded hood, when you twist the focus ring, the hood rotates with it.
Nice in the hand, due to the small diameter at the base.

Disadvantages: The stub is really not enough, on the crope it is difficult to shoot from the hands.
5.6 - a bit dark.

Comment: The lens is good undoubtedly, good sharpness since the open, it becomes a little better if slightly covered. Ideal for weight and size indicators. I chose between this and 300 4.0 IS L, yet I decided that the extra 100 mm would be more popular.