It's a depth of field effect. I don't like it either, and I wish at the very least you could control it.

It bugs me that you get a good look at your guardian's face only once. Sure, they show up helmetless in a few other cutscenes, but one of the most expressive ones you can only once as well--on your way to the Reef. (And it's interesting that they have you piloting a ship without a helmet. I guess ships don't crash as often as they did in Halo.