When you increase the width of the aperture of a lens (your pupil) you decrease the depth of field in sharp focus. It's a fundamental limit of optics.
On a bright day you have a lot of light and your pupil is narrowest, bringing as much as possible into focus.
> So I think doing accurate 3D requires simulating the way in which the brain picks out objects at different depths, but this can't be done simply by offering one depth of field for all viewers, since our eyes can't bounce back and forth alternately focusing a near and far object and creating the increased acuity we get in normal vision.
I watched the Hobbit in 3d and thought it was awful. You had this tiny sweet spot right where the director intended you to look and everything else was a sea of blur.
I realized that I like looking at sets because I was frustrated every time I tried.