Here's a good recent in-depth interview with Emmanuel Lubezki.
One of the Greatest Cinematographers Ever: Gravity‘s Emmanuel Lubezki
This is the first film you shot entirely digitally—how did this change your process?
I’ve been working with digital cameras for a while, but I’ve never done a fully digital film. When we started doing prep for Gravity and began figuring out how to shoot it, we quickly realized that film was not an option.
That had to do with what happens with the film grain in 3D, because the film grain lives in a very specific place in the depth of 3D that just looks weird. It almost looks like a curtain, so we couldn’t use film. And then the other thing we realized is that because of how long the shots are, and how complicated it was going to be for me and Alfonso to be near the actors, we liked that digital cameras and their monitors allowed us to have a very good idea of how the film was going to look and what the actors were doing. We could really watch, with very high detail, their expressions. Also talking to Tim Weber [Gravity’s VFX supervisor] about the fact that we were going to do all the digital compositing, we realized we had to do the movie digitally.