This isn't a question, but more of a comment of appreciation and discovery.
I was working on a video for a client who after I delivered the video in 1080p asked for a 4K version. 4K was never stated as a requirement and a good part of the footage was shot at1080p for potential slowing down. It was edited on a1080p timeline.
After trying to explain to my client why upscaling was a bad idea I decided to export a version in 4K (using the YouTube 2160p 4K Ultra HD preset in Media Encoder) out of curiosity. I was very pleasantly suprised at the result! It is noticeably sharper than the same version at 1080p (YouTube1080p Full HD preset). Also sharper than the version exported in ProRes in1080p.
I was wondering if anyone else has experienced this and or sees any potential pitfalls with making these "4K" videos that were edited in 1080p?
If you're thinking that looked good, definitely look into using the Detail-preserving Upscale effect in After Effects to get from 1080p to 2160p.
After Effects User Guide > Detail-preserving Upscale effect
Live action footage can be fairly fogiving, looking okay even without using an upconversion algorithm.
If you have titles and lower 3rd, look into Video Enhance AI by Topaz Labs (Video Enhance AI – Video Quality Software (topazlabs.com).