Chris Sohl, who captured this image from Bungie's Halo 3 announcement trailer, had this to say about it:

I'm a photo restoration artist, and I decided to extract the clearest picture of Cortana and clean it up from the weird lighting effects. Here's the result. This is the first and best look we have at Cortana in Halo 3, and she's lookin pretty cute... for an AI... *This is not technically a true screen capture; it's about 15% rendition and substitution.