Ray tracing obviously adds a lot to visual fidelity in terms of lighting, but it's also quite a demanding technology which can affect performance dramatically. With everything else Metro Exodus does to push the hardware in the extreme preset, it's not surprising to see that capping the framerate at 30 fps does not even guarantee it will remain steady in 4K in some areas of the game. We've prepared a comparative video showcasing RTX with DLSS off. Enjoy!
Update: 4 videos added, among which one new comparison between RTX High and no RTX and a 1440p/60fps video in ultra and RTX set to high.