Viewing is platform dependent. Video cards, monitors, and drivers. Not only resolution but how it decodes compression (when applicable), color balance, transition between pixels. Some 4K monitors appear sharper than some 8K monitors because the contrast between pixels is greater (so I've heard as I have yet to dip my toes at that end of the spectrum yet) My laptop says 2160 4K, but something can't keep up and the video is choppy. Plus the screen is not that great and the resolution would be wasted. Unfortunately my eyes are larger than my wallet.
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