“Avatar” may give some audiences shocks and thrills as 3-D characters and explosions spring out of the screen, but errors in the way 3-D images are presented and perceived by human eyes may also give viewers fatigue and headaches, problems that U. California-Berkeley researchers are trying to correct.
At the campus Visual Space Perception laboratory, researchers are studying problems common to 3-D effects used in movies and televisions and are developing technologies to fix such issues on smaller scales. Problems with the delivery of 3-D imagery manipulate the way the eye perceives images and cause people to experience physical discomforts.
According to Martin Banks, principal investigator for the lab and a campus professor of optometry, one of the biggest problems experienced by 3-D imagery is called the “vergence-accommodation conflict,” which has been known to cause headaches, tired eyes, blurry vision and fatigue because viewers are forced to fight their “natural system.”
When eyes look at an object, they must first focus together on that point – referred to as vergence – as well as “accommodate” the object, focusing in like a camera lens, Banks explained.
“The brain kind of links them together so that if you affect one of them, it drives the other one,” he said. “That’s the way the real world works, and so it’s a good thing these things are coupled.”
But 3-D images are different, Banks said. The light from the image comes from the same place – like a movie screen – but the images appear at the screen level, behind the screen level or appear to jump out of the screen. This creates a conflict because the point where the eyes accommodate the light is fixed at the screen level while the eyes converge to focus the image wherever the image appears to be.
The lab developed a way to reconcile this conflict using two mirrors, two lenses and two computers, but Banks said such technology could not be used on a large scale because it is too complex and expensive.
“For some special applications, like a surgeon looking at a stereo microscope where it’s only one person you care about, then it’s reasonable,” he said. “I think it makes sense for single-user applications, maybe even for video games where there’s usually only one person playing.”
Banks said 3-D television and movie producers could actually do a service for people who are unaware that they do not have stereo vision – necessary to see 3-D effects – by running tests before programs.
As 3-D technologies continue to develop and expand in their mainstream presence in movies, video games and now television, the long-term impacts of such visual effects remain uncertain, Banks said, especially if people begin spending multiple hours in front of a television screen compared with an hour or two at a movie.
“I don’t see a smoking gun, something where I’d go ‘Wow, we’ve got to really be worried about this,'” he said. “The only one I really wish we knew more about is kids because kids aren’t always monitored so well … You can imagine a 6-year-old, a 7-year-old, a 9-year-old sitting around and doing this stuff for hours and not telling their parents.”