I think the D5 is supposed to have the finest AF system, ever.
Why can't you use a monopod with it for weddings?
I don't know what the D5 has - it's not out yet. Certainly, the 1Dx has the fastest AF in Canon's lineup (both in terms of acquisition and tracking), but not the most precise.
They don't usually use monopods beccause they're shooting at all sorts of angles - low angles, high angles, crouching, standing over people, etc. in quick succession, so constantly changing the height of the monopod is impractical.
Good point, but here again you're talking about shots taken in ideal, selected conditions.
As are you.
When you're not shooting 14fps or tracking fast action in the dark (the minority of shots, unless you shoot nothing but sports) the D4/1Dx's features are completely useless. You could get exactly the same shot with any other camera.
On the other hand, the resolution deficiency shows up in every single shot - stitching aside, no matter what you do, you can never get a 36MP image out of a 20MP sensor.
But none of this is the point.
The point was the D5/1Dx is the preferred tool of professional action-sports/nature photographers, not photographers taking photos of people sitting still or moving slowly.
The point is that someone mentioned that the D5/1Dx is
the professional camera, and that, by extension, any other camera is not a professional tool, and that pros shooting using other cameras are not as worthy as those shooting fast action using the D5/1Dx.
I know a guy who travels with a 1Dx and a 7D2. He is a Canon Explorer of Light.
The truth is the 7D2 is just a "me too" camera he pretty much uses to promote for Canon, given his position, but even Ray Charles can see that all of his serious, high-action, low-light shots are taken with the 1Dx.
And while this person extols the virtues of the 7D II (compared to the 7D), even he is quick to point out that the files "aren't the same quality" as the 1Dx.
Never seen this fellow even mention a 5D series, on any of his arctic, wilderness-type excursions, and that is because the 5D'' is just not an action camera.
That's one photographer, shooting in one style, out of how many thousands?
You'd never go without a full-frame body as your primary (whether D4 or D810, depending on whether you need fps or resolution more). But, if you use the D4/1Dx, when you need the reach, you need the reach. That's where the high-pixel-density backup comes in.
I am sure the Nikon D5 and Canon 1Dx2 will broaden the gap between (what are essentially) "static" cameras and action (+ low light) cameras.
Low light capability isn't the unique purview of the action bodies. Probably the best low-light sensor out there - the A7s2 - isn't even an action camera at all. The 6D can focus in darker light than the 1Dx.
The 5D3 and D810 are hardly static cameras - the only current cameras they lose out to in terms of fast-moving subjects are the 1Dx and D4s. And they beat the dedicated action bodies in other areas. Sure, they're slightly (only slightly) worse at tracking fast action than the 1Dx and D4s. But to say they're 'static' cameras is like saying that the D4s is completely incapable of shooting a landscape or still portrait.
I'm sure 8k video will render action stills bodies obsolete anyway. When you can shoot 33MP at 25fps and pull a frame from that, what's the point of a body shooting 20-24MP at 14-16fps? At that point, it's essentially just a 6K video camera that can't quite make the frame rate needed for video.