puredrifting
Major Contributor
It would be pretty pointless to make a 4K viewfinder. The pixel pitch would be so small that it would be impossible to delineate the resolving image. There is simply a point beyond which we cannot judge focus, but there is also a point beyond which any technology cannot present focus. If the pitch is too tight, then bleed between the pixels eliminates resolution.
Realistically the only way to judge 4K focus accurately is with a 27" or larger 4k monitor. I shot a PBS special with a 4K camera and the director was using the 20" Panasonic broadcast 1080p monitor and between the two of us, we both had a hard time judging when things were in sharp focus. Peaking in the 1080 VF helps of course. Mitch is correct, pixels are meaningless without the ability to resolve and delineate the image, the same reason that 4K televisions are pointless for most consumers at most typical viewing distances. https://carltonbale.com/does-4k-resolution-matter/