NEW YORK — From Hollywood studios to Japanese TV makers, powerful business interests are betting 3-D will be the future of entertainment, despite a major drawback: It makes millions of people uncomfortable or sick.
Optometrists say as many as one in four viewers has problems watching 3-D movies and TV, either because 3-D causes tiresome eyestrain or because the viewer has problems perceiving depth in real life. In the worst cases, 3-D makes people queasy, leaves them dizzy or gives them headaches.
Researchers have begun developing more lifelike 3-D displays that might address the problems, but they're years or even decades from being available to the masses.
Theater owners including AMC Entertainment and TV makers such as Panasonic are spending more than a billion dollars to upgrade theaters and TVs for 3-D. A handful of satellite and cable channels are already carrying 3-D programming; ESPN just announced its 3-D network will begin broadcasting 24 hours a day next month.
Yet there are already signs that consumers may not be as excited about 3-D as the entertainment and electronics industries are.
3-D TV sets were available in the United States for the first time last year, but shipments came in below forecasts, at just under 1.6 million for North America, according to DisplaySearch. Nevertheless, TV makers such as Samsung and Panasonic are doubling down on 3-D and introduced more 3-D-capable models this month at the International Consumer Electronics Show in Las Vegas. Those models cost more than regular ones and require glasses, just like in theaters.
Research into how today's 3-D screens affect viewers is only in its early stages. There have been no large-scale scientific studies.
Nintendo says children 6 or younger shouldn't play with its upcoming 3DS handheld gaming system with 3-D technology, because it might affect vision development.
3-D screens and glasses create the illusion of depth by showing different images to each eye. That simulates the way objects that are at different distances in real life appear in slightly different places in each eye's field of view.
That's enough for most of us to perceive a scene as having depth. But our eyes also look for another depth cue in a scene: They expect to need to focus at different distances to see sharply.
More specifically, our eyes track an approaching object by turning inward, toward our noses. The problem is that as the eyes turn inward, they also expect to focus closer. But a screen isn't moving closer, so the eyes have to curb their hard-wired inclination and focus back out. This mismatch between where the eyes think the focus should be and where the screen actually is forces them to work extra hard.
"That causes at least part of the discomfort and fatigue that people are experiencing," says Martin Banks, an optometry professor at University of California in Berkeley.
The problem is magnified if the screen moves close to the viewer — exactly what's happening if 3-D viewing moves from the movie theater to living rooms to game gadgets like the 3DS.