Need help understanding 1080p Vs 4K Video download quality

[Lycop]

Hi.

I have a question regarding Video file sizes and resolution.

My current TV supports 1080p. However I plan to get a 4K TV soon.

I am downloading Video files (.mp4) from a couple of sites. The sites offer the files at two resoultions - 1080p & 4K (among others).

The 1080p file is usually around 500Mb while the 4K file is around 1.6-2 GB.

Firstly, will the 1080p version be "upscaled" automatically to 4K by a 4K TV or will it display it at 1080p instead?

If it will be upscaled, would I be able to see a noticeable difference between the "upscaled" 1080p version versus a 4K version of the same file on a 4K TV?

Also, what file size ratio - in terms of file sizes between a 1080p and a 4k video - would be considered worth it to download the 4k size which
is larger in size and more difficult to store?

Meaning, should the 4k Video be at leat twice as large as the 1080p Video? 3 times? 4? At what ratio would it be worth the while to download the 4K file?

Hoping someone can help.

[ConsumerDV]

Do you not have similar questions when playing DVDs?

[Cornucopia]

Unless you tell your computer or media player otherwise (usually via AV Mode or Display Mode settings), one or the other (or occasionally both) will upscale whatever it is given in order to fill the screen.
So the answer to automatic upscaling is "usually, yes".

Whether you see a noticeable difference depends on a lot of factors: the quality of the provenance (its history) of the file(s) and whether the proper settings were used or not. Also, it would not look very different if the "4k" version was itself previously upscaled at some point. Assuming some trust of legitimacy and professionalism is there, then it comes down more to whether the 1080p and the 4k files were each optimally compressed. But let's say for the sake of argument that they are. And since the 4k is 4x the resolution of the 1080p, it is not out of the ordinary for it to have similarly increased bitrate requirements (though not usually exactly 4x, as there is more efficiency when having more pixels to reference).
After all that, if they are both "optimal quality" for their resolution, AND if you are sitting close enough to be able to visually tell the difference between those 2 pixel densities, then YES you should be able to see an improvement in the 4k version.

Maybe this reference image, that I have used before, would help you visualize that...


The image is subdivided by its resolution in that column, with the numbers corresponding to the (vertical) resolution of that column.

Scott