Question about 4k sequences scaling and output and computer performance

[goguvarra]

Hello,

I've been reading on the forums that:

Original footage being 4k and working in

1) 4k sequence and exporting 1080p -> you lose quality when scaling the original 4k material

2) HD sequence and exporting 1080p -> you don t lose quality when scaling the original 4k material

3) HD sequence and exporting 4k -> you lose quality when you do this

well I tested this and tried all the options above...and the result looks the same for all 3.

Granted, I have an HD monitor so for option 3 maybe i'm not able to see the loss in quality?

For 1 and 2 I tested this by scaling the footage the same in both the 4k and HD sequences. I scaled the footage pretty much so all the defects show up but the end result is identical.

What am I missing?

The threads that I've read regarding this are these:

https://community.adobe.com/t5/premiere-pro-discussions/4k-footage-in-hd-sequence-will-it-lose-origi...

https://community.adobe.com/t5/premiere-pro-discussions/output-to-1080p-4k-footage-edit-1080-or-4k-s...

Will working with 4k footage in a 4k sequnce tax my computer more than working in a HD sequence with the same footage?

Thanks

[Ali Jaber]

You don't lose quality in case 1 where you scale down 4K footage. In the thread you mentioned the original poster was scaling down a 4k footage in a Fhd sequence then exporting in 4K, so yes, he loses quality.

[goguvarra]

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@Ali Jaber wrote:

You don't lose quality in case 1 where you scale down 4K footage. 

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Sorry, I realise now my phrasing was not correct. 

in case 1 - I mean scaling the 4k material from the effects control panel. Like scaling above 100.

As I understand you lose quality doing this in a 4k sequence as opposed to an HD sequence, but I cannot see any loss of quality. This is what I do not understand

[Steve Griffiths]

to add to ali_jaber's post ...watching any of your above exports on an HD monitor will effectively look the same and none will be 4K image quality. And option 3 is a waste as all you are doing is scaling an HD image to 4K but only getting the resolution of HD in the final product.

Working with any 4K material (regardless of what sequence it's in) will tax your computer more than working with HD source material.

Working with 4K material in a 4K sequence and applying effects (plugins, lumetri etc.) will tax you computer more than if you put 4K footage into an HD sequence. Remember that 4K is basically 4 x the pixels of HD ... so lot's more processing by your computer.

The decision you need to make is - do you need 4K exports or is HD good enough. And this is based on the end use of your programs and their content. In most cases, at the moment, I would suggest HD is probably going to be OK (but really depends on a lot of factors). But if you want to stay in 4K all the way, look into things like using proxies in Premiere Pro IF your computer lags when working in 4K. Proxies can speed up the editing process. However a 4K sequence will still take longer to render and export than an HD one.

[goguvarra]

...watching any of your above exports on an HD monitor will effectively look the same and none will be 4K image quality.

But why? Everything I'm reading says that 1 should look worse than 2 because I've zoomed the 4k clips inside a 4k sequence? 🙂

And option 3 is a waste as all you are doing is scaling an HD image to 4K but only getting the resolution of HD in the final product.

So if you put the 4k clip inside an HD sequence it basically treats it as HD? So it doesn t matter if i choose the native UHD resolution of the clip at the export panel, the quality has already been lost?

I think I'm not understanding how sequences work internally 🙂 

And I can't see any loss of quality but for example 3 i think this is because i don't have a 4k monitor to compare an UHD export from a 4k sequence vs my UHD export from a HD sequence, right?

*why can't I edit my own posts anymore? did they change the interface? this is annoying 🙂

[Steve Griffiths · Accepted solution]

OK I think I understand a bit more of what you mean.

If you put a 4K image into a 4K sequence and scale (zoom) that image up (let's use 200% as the amount of the scaling) then yes, you have lost image quality. In fact in this case, what you have is now is (*almost) exactly HD (1920x1080) quality within a 4K sequence. If you export that image and watch it on a 4K monitor it will appear (visually) as HD quality. IF you watch this 4K clip on an HD monitor you'll see it in approx HD quality ... because the clip had become approx HD resolution in a 4K sequence.

Now if you start with an HD sequence and drop a 4K image into it and the 4K image fills the frame - yes it will be HD resolution because in an HD sequence can only show 1920x1080 pixels so it averages all the pixels from your 4K image into HD resolution .... BUT you can scale this image up to 200% (while editing) before you will lose any quality at HD resolution. Once you pass 200% the quality of the image will degrade and now be less than HD quality (in the HD sequence) because you have 'zoomed' in beyond the area within the 4K image that contains 1920x1080 pixels.

To directly answer your question: if you put a 4K image into an HD Sequence you can never have more than HD resolution in the exported video, even if you export it in 4K. Rule of thumb - always export at the native resolution of your sequence. You can export at a smaller resolution and get the video at whatever resolution you choose (say 1280x720) but never export at a higher resolution than your sequence - it's a waste of space and gets you no benefit.

The advantages of working with 4K in an HD sequence is that (up to 200%) you can scale the image and reframe the shot as much as you like and still get HD quality exports. Doing this (say) with an interview is something we do all the time. With one (4K) shot we can have a wide and a tight framing of the subject from the one camera.

Side note: ensure when 4K clips are in an HD sequence that you use 'set to frame size' rather than 'Scale to frame size' (you find this in a drop down menu if you right click a clip in your sequence) ... and while I've been talking about 200% scaling - once a 4K clip in an HD sequence is 'set to frame size' you'll notice that in the 'Effects Controls' panel the clips 'scale' will appear as '50' (this is a percentage) when you have your 4K clip filling the HD frame ... and you can safely take the scale of this clip up to 100 (%) and lose NO quality in the HD sequence.

* pixel averaging will occur at different scale settings and image positions reducing actual resolution slightly.

[goguvarra]

1) 4k sequence and exporting 1080p -> you lose quality when scaling the original 4k material

2) HD sequence and exporting 1080p -> you don t lose quality when scaling the original 4k material

Just to be clear, I meant scaling the 4k material inside the sequences, wether its a 4k or an HD one, from the effects panel.