Question about video resolution: Why do my 1080p encoded videos show up correctly but my 2160p encoded videos show up so much darker.

This has been bugging me for a while now, windows 10, new motherboard, HDMI to 4k tv [600 nits], intel uhd on board display adapter running at 60hz, when I play a 1080p encoded video with, for example, Windows Movie and TV app, it plays fine, but when I play the same move or show in a 2160p encoded video it shows so much darker...