Believe me when I tell you, Tero, I’ve done it all, I know all the quirks. First off contrary to what I’ve read in different places, including Nikon’s website, ALL Nikon dslr’s do NOT output 24p. My D5500 only outputs 29.976. Then again, Atomos says it doesn’t matter what the Ninja 2 says is the video mode, it will record the video mode your camera is putting out. Not true. I’m putting out 1080p 24 fps but it records 1080p 29.97 fps.
One supposed workaround is to set HDMI output to AUTO instead of 1080p (which is the only way you can get the Ninja to allow choosing different video modes) but, as I said, it seems to think AUTO means 1080i at all times.
I read of a tweak where if you start recording on your camera, you can cheat the Ninja into recording 1080p 23.976 fps. That only worked once. I never know what I’m gonna get out of this thing. It seems the only way to be sure is set HDMI output to 1080p and set video output to 1080p 24 fps (or 29.97 fps. Doesn’t matter. The Ninja is going to record 29.97 fps).