Essentially they have much better resolution source material and they scaled that into a 4K signal which allows for a viewing experience that is "better" than having it be scaled to 1080P.
As for showing it on the web? Well generally unless you have a 4K monitor you won't see it at the full video resolution. It does look pretty crisp and stunning at 4K.
Ah this is a common misconception actually! I think that the chroma resolution in video is often less than the pixel resolution, so a pixel resolution higher than your screen resolution can still be useful to get the extra colour data.
I feel like I'm missing something here. A display that has enough pixels to show the pixel resolution of the source should be able to resolve all the (subsampled) chroma information as well, should it not? (Er, at least as long as the subsampling is done at an integer divisor of the original!)
Anyway, a high-resolution source could look better than a low-resolution source when displayed on a display with the same resolution as the low-resolution source for a number of reasons, perhaps the most obvious being that the high-resolution source might be of higher bandwidth.
If you have a 2k screen, you may think there's no point watching a 4k video instead of a 2k video. Well there is even if you ignore bitrate - because the 4k video when resized to 2k will contain more colour information than the 2k video shown at 2k.
> A display that has enough pixels to show the pixel resolution of the source should be able to resolve all the (subsampled) chroma information as well, should it not?
Yes, but the point is that a display that does not have enough pixels to show the resolution of the source, will be able to show colour per-pixel in the 4k video, rather than colour per-every-other-pixel as it would in the 2k video.
(Chroma subsampling is not this simple in practice.)
I have noticed this with quite many video players. Downscaling from 4k to fullscreen on my not-so-4k monitor seems to provide better details than the native 1080. On YouTube for example. Do you know if this is in effect for YouTube videos?
Big factor here is the bitrate of the video; on practically all streaming platforms 1080p video is very heavily compressed and while speculating, on sites like YT there is also encoding speed vs visual quality optimization going on.
With equal bitrates and high-quality encoders the difference should be smaller, or even turn towards preferring 1080p depending on the bitrate.
True, although for this particular video I was more impressed by the high frequency edges of the mostly monochromatic moon surface. The edges of craters are very sharp on a 4K screen.
As for showing it on the web? Well generally unless you have a 4K monitor you won't see it at the full video resolution. It does look pretty crisp and stunning at 4K.