The other fascinating thing about that film was working in three dimensions. The way we did it back then, which is still the way we do it today is, you don't edit in 3D all the time. You edit in 2D. And then, at certain intervals, you will say, 'All right, let's watch it in 3D, and see if we made any mistakes', because you can make mistakes, not only editorial mistakes, but mistakes in the translation from 2D to 3D. And so all week we would edit in 2D, using one of the sets of work print, what we called 'the left eye work print.' Over there was a rack of film, which was the right eye, which was the same material, but seen from the other lens of this 70 mm monster that we were shooting with. And my assistants would conform the right eye to the left eye.

And then, on Friday we would screen what he had looked at. And I noticed a curious phenomenon, which was that material that looked perfectly fine in 2D would not look fine in 3D because of  the lateral displacement of the image. Say, Michael Jackson doing 'moonwalk' left to right, would look in two dimensions, perfectly smooth. When you looked at in in three dimensions, it was in three dimensions. But all of a sudden it stuttered, so that it was a version of the thing you see in Western movies with the spokes of the wagon wheel going backwards. There was some threshold that was being exceeded in three dimensions that was perfectly fine in two dimensions.

What that is, I think, is the fact that in three dimensions your brain has to pay particular attention to the edges of things, to line them up correctly, so that the three dimensional illusion takes place. In two dimensions, yes, you see the edges of things. But your brain is not obsessively concerned with the edges of things. It is in three dimensions, and as a result, the stuttering effect that I'm talking about, which is there in two dimensions, but it's kind of ignored by the brain – suddenly that looms up as a problem. And this was what caused Peter Jackson to shoot the Hobbit films in 48 frames.

It's an acknowledged problem, this stuttering issue. And so he [Peter Jackson] hoped, in fact, and did overcome much of this by shooting at an advanced frame rate. So that the brain is being supplied with more information, so that it doesn't have to obsess so much about the edges of things. I'm simplifying a little bit. But that's essentially the problem. The 48 frames, of course, brings along another set of problems, which is that the image has even more clarity to it.

And if you're not careful, those films are criticised, as the Hobbit films were criticised for looking like actors in costumes on a set, rather than the characters in a world. And that gets at a very interesting flex point between reality and illusion that when we watch a film, we project onto the film what we want it to be, until the information from the film tells us that we've gone too far, or that that doesn't work. And in a sense, shooting at 24 frames a second, or 25, or whatever the system is that we use, Europe and America are different... Supplies a certain amount of information, but not too much. And that lowering of information allows the projection of: I want to believe this is Frodo there, not an actor in Frodo costume on a set. And as long as there isn't too much information, I can receive it. So this is partly one's concern in making a film.