Unexpected Problem with 3-D Movies

I’ve posted before about the unfortunate side-effects of 3-D movies, such as their tendency to cause headaches and nausea in some viewers. However there is one side-effect that I never would have predicted.

According to this story, a U.S. serviceman came back from a tour of duty in Iraq and found that his wife was pregnant. She denied having an affair and explained that she got pregnant from watching a 3-D porno movie.

The husband seems willing to believe her, saying “I see it as suspicious. The films in 3D are very real. With today’s technology, anything is possible.”

(OK, I admit that this story is probably entirely bogus. TechEYE doesn’t strike me as the sort of publication that does rigorous fact checking, and they don’t give any source for the story. What can I say? Some stories are too good to check.)

The Problem with 3-D Movies

The movie industry is thrilled with the first-weekend box office success of Monsters vs Aliens and is convinced that 3-D movies of this sort are the wave of the future. Well, I never claimed that my reviews reflect popular tastes. Nevertheless I remain convinced, based on my own experience, that this sort of stereoscopic imagery is a gimmick that actually detracts from the movie-watching experience, and I don’t think it will succeed in the long run.

I think I have figured out what the problem is, though this is just speculation and I don’t have any solid scientific evidence for it.

When you first look at a movie like Monsters vs Aliens it initially looks very “real”, like looking at a scene through a window. Most descriptions of the experience never go much beyond that initial impression.

However there is an important difference: when you look at a real scene, or for that matter at a hologram, and you move your head, the image will shift with nearer objects moving more than more distant objects. With a stereoscopic image you can move your head all you want, and the image will remain unchanged. The part of the brain that processes this kind of distance information finds this very unsettling.

When you look at a normal “flat” projected image, it also doesn’t change when you move your head, but that’s no problem. The low-level neurons that infer depth from parallax shifts know that it is a flat picture and shouldn’t change. The ability to infer depth in a flat image based on perspective cues is a higher-level brain function and is to some extent learned. (Dogs and cats have stereoscopic vision, but they generally ignore the TV screen because it’s just random patterns of light to them; they can’t see it as a three-dimensional image.)

I noticed that to avoid the disturbing behavior of the stereoscopic image I was unconsciously holding my head rigid. The strain of doing this was probably why I got a headache.

If this analysis is correct then Hollywood needs to forget about stereoscopic projection and concentrate on developing some sort of system for holographic projection. This of course will require numerous technological breakthroughs, so they had better get cracking.

UPDATE: Daniel Engber makes much the same point in greater detail. His explanation is a bit different from mine, but I think the bottom line is that there are multiple perceptual pathways that don’t work right with the current 3-D technology.