Just received this from Adorama, great service by the way and thanks1! Haven't had a chance to use it yet in anger, but initial tests on a 1 Dx and 7D2 indicate that my 300 f 2.8 L IS mk2 may not see much use in future, this lens seems to be sharp as a pin, even with 1.4 and 2x mk3 extenders, and...

Great Glass!

This is a sweet lens! Not only is it extremely lightweight, the images it produces are tack sharp, even at f4! I just shot for 3 weeks in Antarctica with this and it did not disappoint. Great for wildlife and landscapes. Mostly it was paired with my 7D Mark II giving me a boost in lens length.

REVIEW: Canon EF 400mm f/4 DO IS II USM Lens Review

Specification A professional-grade telephoto lens, which sports a moderately fast maximum aperture of f/4, image stabilisation, silent focusing with full-time manual focus override and a relatively compact design, thanks to the use of Diffractive Optics.

Canon EF 400mm f/4 DO IS II USM Lens Review

A professional-grade telephoto lens, which sports a moderately fast maximum aperture of f/4, image stabilisation, silent focusing with full-time manual focus override and a relatively compact design, thanks to the use of Diffractive Optics.

Outstanding sharpness from maximum aperture; Low CA; Low distortion; Relatively compact; Excellent build quality; Effective image stabiliser

Price puts this lens beyond the reach of many