How 4K DSR works or scales?

[skipsneeky2]

Got a new 1080p monitor,got some titles that are less demanding that i want to try out 4k on with my 970.

Titles like WOT and the first Bioshock run absolutely fine,hud and the image appears to be the same size as 1080p yet the image appears sharper.Is that normal for 4k DSR?Other DSR resolutions like 1440p always appear way to small for a 23''.

Hoping anyone could help me out

 

[Pottuvoi]

Here is the basics.
http://www.geforce.com/hardware/technology/dsr/technology

So it changes the scale of rendertarget and scales the result with 13-tap gaussian filter to final frontbuffer size. (screen)
Advantage of this method of downscale is the ability to change the size of filter kernel. (smoothness)