Maybe I'm being a moron but I did (8,294,400 - 2,073,600), then divided the result by two and added it on to 2,073,600 to get 5,184,000 and 1701p gave me the closest I could get to that.
So its more the midpoint between 1080p and 2160p, pixels wise, as a better way of evaluating how image quality increases as you increase res, rather than looking at the percentage both axis have increased, which would give roughly 1530p as the midway point.
Now I'm questioning it tho haha, maybe I'm going mental.
