Жиденькие оправдания с офф-сайта:
[quot]One area I thought I might have a problem with is the loss of focusing at f/8. The previous [camera], the EOS-1D Mark IV can focus from the centre point when using an EF500mm f/4L IS II USM (or EF600mm f/4L IS II USM) and an EF2x III extender or EF800mm f/5.6L IS USM and an EF1.4x III Extender, but the EOS-1D X cannot. A lot of people have been talking about this as a problem. The reality is that, in use, I have not found it a problem at all. I have found that if I need that focal length, then I should either be moving closer to my subject, or I can use manual focus accurately. The viewfinder is so clear that it is easy to see when something is sharp in the frame, and the new magnify button, which I have set to 100%, makes it very quick to check that I got the focus right.
Besides this, I always found focusing at f/8, or with extenders fitted, was a little slower than normal, so the only time I’d really use it is for shooting static subjects like bird portraits – and, for this, manual focus works perfectly. Equally, for me, this requirement is the sort of thing I only need a couple of times a year at most, so I can easily work around it by shooting with the lens I have and then cropping afterwards because the detail and resolution is so good. It is honestly not a problem.”[/quot]