Vergence-Accommodation Conflict: Why Bad 3D Literally Makes You Sick

If watching 3D content has given you a headache or even made you nauseous, you’re not alone.

Good 3D requires a surgical level of scientific precision to pull off accurately. Unfortunately, many industry professionals openly acknowledge that there is significantly more bad 3D on the market than there is good 3D. That fact doesn’t help an industry trying to get a viewing population to embrace a technology that it has proved hesitant to accept.

“I would argue that viewer discomfort is perhaps the biggest issue between widespread embracement of stereo 3D,” Dr. Martin Banks, professor of optometry and vision science at University of California, Berkeley, said during the recent Content & Communications World summit in New York.

Although scientists point to numerous causes for 3D-viewing discomfort — misaligned images, incorrect viewing position, vertical-vergence eye movement (where looking at a 3D image sideways can actually force one eye to go up and the other eye to go down) — the cause with the most substantial set of research behind it is referred to as “vergence-accommodation conflict.”

According to Banks, a person looking at the world through two eyes has to make two kinds of responses with those eyes. First, the brain converges the eyes so that both are directed at the point of interest (that’s called vergence). It also has to focus the lens within the eye to sharpen the image on the retina (that’s accommodation). As a result, if the brain and eyes mis-converge, the viewer will see double images; if the brain and eyes mis-accommodate, the viewer sees blurry images.

As much as 3D movies and television shows try to emulate a real-world viewing environment, it’s simply not the same. In the natural environment, the distance to which one has to converge and accommodate are the same because, usually, you are looking at and focusing on the same object.

“So it stands to reason that the brain has yoked these two signals together,” said Banks, “and it turns out that, when you converge your eyes, that causes the eyes to also focus and, when you focus your eye, it causes the eyes to also converge. So the two systems actually speak to one another. It makes perfect sense in the real world because they are driven to the same distance, so why shouldn’t they aid one another?”

It’s nearly impossible for a content producer to know exactly where on the screen a viewer’s eyes will be looking. Sure, attention can be drawn to a main focal point, but viewers’ eyes tend to wander, absorbing supporting characters in movies or checking out the defense during a football game.

Unfortunately, most 3D images displayed on televisions and movie screens across the country have trouble perfecting this art, forcing the viewer’s brain to make adjustments that it is not comfortable making. That leads to a painful and, at times, nauseating experience.

Major producers of 3D content understand the pressure that comes with each 3D broadcast that hits the air. If average TV-viewing Americans are to be persuaded to take the plunge into buying a 3D-movie ticket or a 3D-capable television, they need to experience the product. However, one poorly executed 3D production, and those physically ill first-timers may never come back.

“If you do something bad in 2D, it’s going to look bad on the screen,” said Pete Routhier, VP of 3D product strategy and business development at Technicolor. “If you screw up in 3D, your viewers are actually going to feel bad, and that’s a very significant difference because this is the first time that we have a display technology that has such a high capability of making your audience sick.

“3D glasses should be a part of the experience,” he added, “but air-sickness bags and Tylenol shouldn’t.”

Most modern 3D, including sports, is shot using a rig with two side-by-side cameras; a technology director James Cameron helped invent for the wildly successful 2009 film Avatar. The viewer’s brain is than tricked by showing the left eye one image and the right eye another. The brain then layers these images together and produces a 3D image.

While the rig is both cost-effective and allows for a more efficient fusion of the two images, live 3D sports is fraught with potential 3D-viewing violations. With its fast-moving action, quick cuts, and the potential for people’s or objects’ jumping in front of the camera at any given time, some sports viewers are in for a bumpy ride that may leave them wanting to keep the wings and beer on the other end of the table.

What’s worse, there may not be an overarching scientific solution to the problem. Although a wealth of work and research is still to be done, ocular science has exposed a glaring challenge for those producing 3D content: everyone experiences it differently. In fact, Routhier added, 4%-5% of the population cannot even see the illusion of stereo 3D because of health issues. There is also another percentage that just doesn’t feel well when viewing 3D at all because of health concerns.

Concluded Banks, “We’d better understand [the challenges], and we’ve got to learn to deal with these issues.”

Until then, the dream of a fully 3D television and movie market remains just that, a dream.