If you thought something looked a little off in the multiplayer for Killzone: Shadow Fall when compared to the single player, you'd be right. Digital Foundry has recently discovered that Shadow Fall's multiplayer uses a 960x1080 framebuffer and runs closer to 50fps than a full 60fps.

Now, there are some mitigating factors here. Shadow Fall uses a horizontal interlace, with every other column of pixels generated using a temporal upscale - in effect, information from previously rendered frames is used to plug the gaps. The fact that few have actually noticed that any upscale at all is in place speaks to its quality, and we can almost certainly assume that this effect is not cheap from a computational perspective. However, at the same time it also confirms that a massive reduction in fill-rate isn't a guaranteed dead cert for hitting 60fps. Indeed, Shadow Fall multiplayer has a noticeably variable frame-rate - even though the fill-rate gain and the temporal upscale are likely to give back and take away fixed amounts of GPU time. Whatever is stopping Killzone from reaching 60fps isn't down to pixel fill-rate, and based on what we learned from our trip to Amsterdam last year, we're pretty confident it's not the CPU in this case either.

NeoGAF user, ArchedThunder, gives a good breakdown of what's happening with this resolution thing.
Some people seem to be a little confused at the resolution thinking that it upscales from 960x1080 to 1920x1080 like you would upscale a sub 1080p game to 1080p, it doesn't. I made some images to help.

Okay, so let's say the red lines are what is being updated while the black lines are empty space.

Now this is what it looks like on frame 1
On frame 2 this is what it looks like

And when frame 2 comes it it blurs the information from frame 1 to fill in the black spaces. This is why it looks fine when standing still but looks blurry and odd in motion. If we could take a single frame of KZSF's multiplayer with this effect turned off it would look something like this.

Zoom in to see the full effect.

The grey lines are dead space where nothing is being rendered on this frame.

So techinically the game is rendering at 1920x1080, just not on each frame.

Keep in mind that Sony and Guerrilla Games said prior to the game's release that the multiplayer was 1080p native and 60fps. Neither of which are true. But you can see this for yourself this week as the free week for the multiplayer component to Killzone: Shadow Fall begins tomorrow.