[Update: my mistake, I did mean "secondary mirror", not shutter.]

Wow! If you haven’t seen this great animation by Jeffrey Friedl’s of shots taken by Marianne Oelund, you’re really missing out (click to go to the animation):

Ok, I’ll admit my ignorance, I had no idea that we had a secondary mirror in order to give the AF module some parallax to work with give the AF system more light.

I’ve altered the image so that the green part is the secondary shutter and the red part is the primary shutter (which has been partially flipped up).