The downsampling isn't for fun (Destiny)

by Cody Miller , Music of the Spheres - Never Forgot, Monday, July 31, 2017, 23:14 (2716 days ago) @ uberfoop

(And similarly, I disagree about 1080p images "scaling perfectly" to 4K via nearest neighbor. You can certainly do worse, but there's nothing theoretically "correct" about taking the color at a sample point - i.e. a pixel - and solidly filling a rectangular region with it.)

I never said nearest neighbor, but weird scaling ratios can produce quality loss. This is why if you are aiming for TV, you shoot 1080p or 4K UHD and not 2K or 4K DCI. It might not seem like a lot, but downsampling from 2K to 1080p actually makes it look worse than just shooting in 1080p to begin with. Your best bet is a straight up integer multiple.

This is also why (good) cameras crop their sensors when shooting at a different resolution, rather than scaling from a full sensor image.