Normally, when we decrease display resolution in game, the game becomes blurry. E.g., when you do 1280×720 on a 1080p display.

But when I set Render resolution in game to 50 (960×540), it still seems crisp (look at trees, sky and weapon). Upscaling is off. You can see it in the image.

If I change display resolution to same amount, it looks blurry.

I guess both are not same. What's the differences?