What full frame camera can challenge Nikon D5?

What full frame camera can challenge Nikon D5? - 1

It is hard to tell.

No one has any real life experience using D5 cameras and it may be another year before we will see if it is embraced by working pros who currently have Nikon camera systems.

We also will have to wait to see if Canon comes out with a camera that will replace the Canon 1DX and what quality images it can produce.

In any case, I do NOT see Canon users moving to Nikon any time soon. The cost of replacing all their existing gear is just too high, no matter what benefits the D5 and D500 cameras will bring to the table.

Depends upon the challenge. If it's super-high resolution, then the Canon 5DS R will kick it's but. If it's super high ISO performance, then the Sony A7S II will be the winner. Sports? Then the D5 is probably the king of that hill.