Upcoming PlayStation 4 exclusive Killzone: Shadow Fall takes an interesting approach to frame rate: its single-player campaign runs at a steady 30 frames per second and outputs at a native resolution of 1080p. Multiplayer, however, is different.

Multiplayer also outputs at 1080p native, but the official line from developer Guerrilla Games is that it runs at 60 frames per second "a lot of the time" - that is, in certain situations, when there's a lot happening on screen, it drops below the 60 fps benchmark.

The Dutch developer made the revelation during a developer session at Eurogamer Expo today (you can watch it below). Afterwards, in a follow-up interview with Eurogamer, lead designer Eric Boltjes explained why.

"The reason for that is tricky," he said, in reference to the multiplayer not always running at 60 fps.

"Running 60 has become this Holy Grail. Suddenly people think if you run 60 your game is better. Technically, that's not really true. But what it does do is it makes decisions go from input to on-screen a lot easier.

"So, having a constant 60 is not actually better than having a 'lot of the time' 60. It sounds weird, but it's actually true. Because usually in the moments where we're going to drop framerate, either you're already dead or it's too late anyway."

Boltjes said Guerrilla decided to push the visual detail in Killzone, and accepted taking a hit in framerate as a result.

"I think our game, graphically, especially multiplayer, looks a lot more detailed and vibrant than a lot of the other games we are in direct competition with.

"We didn't want to make any graphical concessions. We didn't want to say, we can run at 60 constantly if we just half the resolution and take out all the destructibility and remove all the glass, for example. We didn't want to do that. We wanted to keep it really pretty and try to make it 60.

"It's just we can't go out and say we're always 60, because that's lying. We're very close. And I challenge anybody to notice, without Digital Foundry looking at it, that there are large drops."

Unlike multiplayer, Killzone: Shadow Fall's single-player campaign runs at 30 fps.

"The reason for that is graphically single-player is even a step above multiplayer," Boltjes explained. "There's even more destructibility.

"We analysed what 60 brings. 60 in multiplayer is really important because your reaction time is a lot shorter. In single-player it's actually a lot longer. It's not because our AI is stupid, but because you simply have more time to react. We said we don't need 60, and we want the graphical push."