Strictly speaking, this wasn't a fair fight.
Nikon D750s don't take 4K video (You can ask Nikon and Canon why even their most expensive DSLRs can't do this, but don't expect them to get back to you right away.)
The test was conducted by downsampling iPhone 4k video to 1920x1080 in a video editor and comparing the results to native D750 1080 video.
(And therein lies the bias: downsampling from a higher resolution usually does wonders for 1080 video.)
Yeah, we know that a 24-megapixel Nikon FX-class camera with a fast lens makes an iPhone look pretty sorry in low light, considering the Nikon's much-larger sensor.
And yeah, we know you can't put a nice zoom lens on a camera phone. (Unless you're a crazy Sony engineer.)
We're not saying that cell phone cameras are as good as DSLRs. They ain't.
But if you're covering a news event in decent light and can get a tripod near the talking head, you may as well leave the heavy stuff at home.
Your 4K iPhone (or Samsung Galaxy S7 or Moto X Pure Edition or LG G5) will do the job just fine. And they all have apps to edit video and can, of course, send that video to YouTube or Vimeo.
Watch the video below and be humbled D750, owners.
(Note: prices quoted in headline are current list.)