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 to the point of making it unwatchable. Pulled up the same show, one in 1080 the other in 2160 and took a screenshot, and am attaching it to this post. Does anyone have any idea why this is happening? The fact I can screenshot it and it looks darker in the screenshot seems to tell me it's not the fault of my TV, but I can't figure out for the life of me, what I would upgrade to allow the 2160p encoded videos to play as bright as the 1080p videos, I know I could mess with the brightness on either the display or the video app, but why should that be necessary (windows Movies and TV app does not have a adjustable brightness, but the "glamour" of the videos it plays beats any other video player out the door, by miles, if you know you know). Cheers.