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You are agree on the wrong thing in your first sentence sorry. You are comparing a 4k upload with a 4k upload when viewing the same video at different resolution. Please compare different uploads as you do with your comparisson in the images. We are comparing UHD/4k uploads viewed at 1080p or UHD  with 1080p uploads

Sorry for the confusion, but I don't understand what you mean I agree on the wrong thing. I do not compare the same upload with itself in different resolutions. Originally I have three different uploads.  Youtube downscales the 2520x1080 clip to 1920x822, check "stats for nerds" by right clicking on the playback. 4k upload is looked at in 4k. What I agreed with in my second post was that there is not much difference when I view all three of my uploads in HD playback on youtube, non-excistant might be a little harsh When I look at your examples there are more details on the 1080p 248 UHD sample then your 1080p 137 no upscale sample

The 6x crop is not 1:1 pixels so difficlut to see, it is in fact as you say 6 pixels describing 1 pixel crops should be 1:1 pixel, no need to do a little crop and then interpolate by zooming in 600%.

It's a 100x100 crop scaled to 600x600 in gimp with "none" set at interpolation, so we can get an idea of what's different up really close (of what I see on my screen anyways)

Glad you are comparing yourself but the comparison might be slightly defective since you realy on sharpening filters on the browser when viewing Youtube videos with 2520 width on a 1080p screen, same thing as the UHD video. Shure you can see a difference but they don't say as much since its different filteres applied on browser when going to various resolutions.

2520 clip doesn't have 2520 width on yt, so don't worry about that. Are you sure about added sharpening by downscaling from 4k in the browser? The 4k playback on youtube looks very similar to my non-upscaled 2520 DNxHR clip, can't say I see any extra sharpening going on. Wish I could see all this on a 4k screen though

So I'm not really sure what to make out of all this, in my experience I have to upscale before uploading to youtube and view it in 4k if I want to keep the quality of my source footage, even if it's not 2520x1080. It's a little silly, yes, would much rather just export and upload in source resolution.

Can you send me the original file you uploaded? I can do the test again, using your files, if you want. It needs to be without interpolation, without sharpening and in a format without much lossy compression, like ProRes or DNxHR.

Didn't read your original post correctly, thought this was about 4k playback also. When I look at my upscaled 4k upload in 1080p I agree with what you said in the original post, the difference is almost non-excistent.

However, I still stand by what I said in my above post. When comparing the clips, I viewed the 3840 upload in 4k. The 4k playback of the upscaled 2520x1080 material looks higher quality than the 1080p playback of the 2520x1080 and downscaled 1920x823 uploads, even though I only have an HD screen.

Here are some examples of the 4k playback vs 1080p (2520x1080 upload) on my screen:

4k


1080p


4k 100x100 crop scaled x6


1080p 100x100 crop scaled x6


4k


1080p


4k 100x100 crop scaled x6


1080p 100x100 crop scaled x6 (notice the red has slightly shifted and is sort of "melting", the yellow on tab on the left is almost gone, red bars in center are gone)

Been lurking for a long time, just registered to post this, I just can't really understand what's going on here.

I've uploaded three clips to youtube in 1920, 2520 and 3840 horizontal resolution. Source clips are 2520x1080 10-bit lossless from a 650D.

Here goes (please mute the sound, forgot to mute those noisy nitro rc cars )

1920  https://www.youtube.com/watch?v=M41l0S_TJ-8

2520 https://www.youtube.com/watch?v=CqfdynevqwU

3840 https://www.youtube.com/watch?v=RsknYTpXGTk

On my HD screen I definitely see a difference between the clips. The 3840 clip seems to have more information in the shadows, and the colors are true to the source clip. Yes, bold statements, but that's what I see on the youtube playback. Check for yourself at 14sec, the red on the lifebouy changes between the 3840 and the other uploads. Also the bark on the trees are more defined on the 3840 clip.

At 33 seconds the 3840 upload handles motion WAY better than the lower resolution uploads, resolution and colors are also way better kept at 38 seconds in.

On average the difference is subtle, but it's there. Sometimes it's not subtle at all, at 38 seconds I really see a big difference. In my eyes, if you want to retain the absolute highest possible quality from a 2520x1080 source to YT, a 4k upscaled upload seems to be necessery (for now).

I have not downloaded these clips from youtube and tested them like 50mm1200s did (anybody is welcome to do that!), but is the actual playback on YT good enough to spot perceived quality differences? I mean at 33 and 38 seconds the perceived difference in quality is obvious. Although I do not know if it's VP9 or h.264.

My workflow is as follows: MLV app -> CDNG -> Resolve. For the 3840 upload i chose a 4k timeline. All clips were exported using "force sizing to highest quality" and "force debayer to highest quality". Exported using DNxHR 444 12-bit. Sharpening is the same (in camera raw in Resolve).