Why 3D doesn't work and never will.
Unfortunately Murch's main argument is just wrong wrong.<p>What he doesn't seem to realize is that your state of focus (accommodation) is just about identical for objects at 10 feet away, 20 feet away, etc., out to infinity.  So if your eyes converge on a screen 80 feet away, and try to focus on an object 40 feet away, that's absolutely fine, because the state of focus for 40 and 80 feet away are virtually the <i>same</i> anyway.  Your visual system can't tell the difference.  This is an experimentally demonstrated fact.<p>That is to say, your state of focus varies only for objects less than about ten feet away.  Focus on a salt shaker three feet away, and yes, the distant horizon will be out of focus.  But focus on a tree about 20 feet away, and the distant horizon will be in perfect focus.<p>For an object to be in focus, the distance from the lens to the film (or in this case, the retina), dr, the distance from the lens to the object, do, and the lens's optical power must obey the lensmaker's equation, (1/di) + (1/do) = P.  In the human eye, do = 0.017 m, and P is adjustable.  Plot P vs. do, and you'll see the P quickly asymptotes as you move beyond around 3 m.<p>There are perceptual issues with 3D, but this isn't one of them, at least in cinemas where the screen is far away.