Roger Ebert, a long-time opponent of 3D and a skeptic of most 3D movies, has an essay in Newsweek explaining why. His opening salvo is typical both of his views on the subject and of his lucid, vigorous writing style:
3-D is a waste of a perfectly good dimension. Hollywood’s current crazy stampede toward it is suicidal. It adds nothing essential to the moviegoing experience. For some, it is an annoying distraction. For others, it creates nausea and headaches. It is driven largely to sell expensive projection equipment and add a $5 to $7.50 surcharge on already expensive movie tickets. Its image is noticeably darker than standard 2-D. It is unsuitable for grown-up films of any seriousness. It limits the freedom of directors to make films as they choose. For moviegoers in the PG-13 and R ranges, it only rarely provides an experience worth paying a premium for.
Judging from the box-office success of Avatar, Alice in Wonderland, Clash of the Titans and now How to Train Your Dragon (which bounced back on amazing word of mouth from initially tepid performance and regained the #1 spot last weekend), Ebert might be preaching to a pretty deserted choir loft. Still, he clearly has a point—several in fact, some more telling than others.
3D is dim, true (I noticed this especially on Clash of the Titans). In fact, each eye gets only half the usual amount of light. Still, that’s a tech problem that can be corrected.
More enduring are Ebert’s objections that 3D is unsuitable for grown-up films—Crazy Heart in 3D, anyone?—and that it limits the freedom of directors to make movies as they choose. How does it do this? Partly because, in one very important way, traditional 2D movies are more like real-world 3D vision than 3D movies.
When you look at the real world with two eyes, your eyes have to choose where to focus: on objects close at hand, far away or somewhere in between. Regular 2D movies can mimic this effect, cueing the viewer where to pay attention, and sometimes redirecting the viewer from one part of the image to another by shifting (or “racking”) the focus. 2D movies can also use “deep focus” to bring the entire field of vision into focus at once.
A 3D movie uses two different points of view to create a fairly convincing illusion of 3D—but there are catches. In reality the entire image is the same distance from your eyes: the distance of the screen. Superficially it seems to your brain as if certain objects are closer and others farther away; in principle, this ought to mean that you could refocus your eyes on closer objects or farther objects—but you can’t. Try to focus on a blurry far-away object, and it remains just as blurry as before.
This wrecks the illusion of 3D, so 3D directors are basically obliged to rely on deep focus, to minimize the problem of seemingly 3D objects you can’t focus on. This, though, isn’t what real depth is like either; in the real world, everything isn’t in focus all at once.
What’s more, by relying on deep focus, the director loses the use of shallow focus and racking focus to guide the viewer’s attention. This is a bigger deal than casual movie watchers may realize, precisely because of the effectiveness of these tools at guiding the viewer experience, often without the viewer even noticing. You might think that Jurassic Park would be even cooler in 3D, but consider, for example, the shot in which Tim becomes aware of the velociraptor behind him: the focus rack from Tim’s face to the alarming silhouette behind the screen, and back to Tim’s terrified face. That’s the sort of thing that doesn’t work well in 3D.
And that brings me to one of the least appealing aspects of the 3D craze: the push to retrofit older films for 3D. Converting 2D images to 3D is and will always be a flawed process, since you have to invent information that isn’t there about what objects look like from different points of view. Does anyone really need to see Titanic in dodgy 3D? Raiders? Star Wars? The Wizard of Oz?