Blurry textures at 1080p

[Ansive]

So I was checking the steam page screenshots and noticed the game looking much sharper. It seems the screenshots are at 4K resolution.

Then I tried to set the game in 4K (exclusive fullscreen) using Nvidia DSR and indeed, the game textures are much sharper at '4K downscaled to 1080p' compared to pure 1080p.

1080p:
blurry [i.imgur.com]

4K downscaled to 1080p (check the building roofs):
sharp [i.imgur.com]
Why is this?

Is there a hidden graphics setting that's making the textures blurred? Some form of AA?

I usually only play in 4K for games that don't support non-blurring anti-aliasing. (TAA is very blurry in many games)

[Ansive]

Apparently at higher resolution textures in games get more detailed because they are closer to the screen, more pixels dedicated to the object (at the same zoom level).
Something about mipmaps and level of detail.

I managed to increase the texture quality of 1080p to be similar to 4K by forcing LOD to -1. Performance is much better.
This introduces a bit of texture crawl/shimmering in movement, but I much prefer the sharper textures.

For Nvidia negative LOD can be forced using NVIDIA Inspector.
- Antialiasing - Transparency Supersampling = 0x00000008 AA_MODE_REPLAY_MODE_ALL
- Texture Filtering - LOD Bias (DX) = -1.0000

Example:
normal LOD [i.imgur.com]
-1 LOD [i.imgur.com]
LOD comparison [i.imgur.com]