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Understanding 1080p vs UHD and scaling
I have a piece of UHD 3840×2160 interview footage. I drop this footage into a 1080p sequence, set to fit (making it 50% scale), then scale it up to 100% giving me a punched in shot on the subject without losing resolution.
Now I take the same piece of footage into a UHD sequence. If I want to achieve the same punch in I need to scale the UHD footage up to 200% which should result in quality loss from my understanding. I do so, then export both versions in ProRes HQ.
When comparing the two on a UHD computer monitor they look identical, there is no quality loss between the UHD clip and the 1080 clip. I have a theory this is because the 1080 clip is scaling 2x on the UHD monitor, where as the UHD clip is scaled 2x inside of Premiere, making the two essentially equal when viewing. The same goes for the reverse, when viewing both on a 1080p monitor they look identical.
My question is then what is the purpose of editing UHD footage inside of a 1080p sequence if they both result in the same outcome. I feel like I’m missing something here as I have always understood that working with UHD in 1080p allows greater flexibility and resolution, but I’ve been unable to see this in my testing.
Any thoughts or corrections are greatly appreciated.
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2 Replies
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Well I have read that 4K footage scaled up is extremely solid. Same with putting 4K footage in a 1080 sequence. Remember 1080 has less total resolution than a 4K frame. So scaling 4K footage in a 4K frame holds up. Much in the same way that SD media did not scale great in an SD frame. We used to say that we could get 110-115% scale on SD footage in an SD sequence,
But with 1080 footage I scale as much as 150% and it still holds up.
With 4K then you can assume that the eye can accept the footage scaled up to 200% with no discernible loss of quality.
Now, imagine what you will be able to do with 8K!!!
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Rich Rubasch
Tilt Media Inc.
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Ha! Yeah, true. I can get behind what you’re talking about, but I’ll throw a wrench in and say that I tried this same scaling experiment with a piece of 480×360 archival. I put it in a 1080p sequence and scaled it to 400%, then put it in a UHD sequence and scaled it to 800%. The footage didn’t hold up well, but was nonetheless identical in project and in export even though one was scaled 400% more!
I think this has to do with the relationship between 1080p and UHD being 2x scale and how you view the footage, but it has definitely made me rethink my understanding of resolution and scale.
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