Research Is Missing on 3D TV Health Risks, ATSC Report Says

Much more research on 3D TV health issues is needed before widespread terrestrial 3D broadcasting can begin, said the interim report on visual sciences that recently was released by an Advanced Television Systems Committee planning team (CED March 24 p1). It exposes huge gaps in knowledge and understanding, along with the Catch-22 issue of what meaningful research can be safely done on viewers of all ages when little is known about possible side effects.

Without useful evidence of safety, broadcasters face the quandary over playing it safe with mild 3D effects that are less likely to cause health problems, and airing dramatic 3D effects that sell the idea of format but are more likely to give viewers headaches or nausea, the report said. One likely option, taking a page from Nintendo’s 3DS, will be for TV makers “to provide 3D displays that will allow end users to adjust the depth information contained in a scene to match individual’s preference,” the report said. ATSC’s planning team thinks 3D TV “provides a significant enhancement” over regular HD, but warns that the “simulation is not perfect and, depending on how the 3D content is created, processed and displayed, the end users’ experience can either be enhanced or made uncomfortable and potentially painful,” the report said.

The report cited “much-conversed negative side effects of watching stereoscopic images, such as watery eyes, visual strain, headaches, and sometimes blurred or double vision. In particular, visual safety issues of long-term effects of watching stereoscopic images are important concerns. Viewers tend to prefer 3D content over 2D, the report said. That’s “only when the 3D version is comfortable to view and any visible artifacts that arise from anywhere along the delivery chain are not annoying in the 3D presentation,” it said.

Creating and displaying 3D TV content “offers many benefits to increasing the viewer experience and enhancing revenue,” the report said. But “it will require more bandwidth, which is scarce and if done improperly, can result in a negative and potentially painful experience for their viewers,” the report said. “Clearly technology can solve many of the issues, but given the subjective nature of the impact of many of the factors, more information is needed to better understand and implement the services."

Particular care must be taken with 3D programming for children, because “the critical period for the development of stereopsis in humans is well-defined,” the report said. “Onset occurs at approximately 3 months of age, followed by a rapid period of maturation until 8 to 18 months of age, and a more gradual improvement until at least 3 years of age.” Little is known for sure about how many in the general population are “stereo-deficient,” the report said. Estimates of how many people can’t properly view 3D range all over the map, it said.

The report rates “disparity magnitude” as one “major potential contributor to visual discomfort” in viewing 3D, because “the closer a stereoscopic object is depicted, the larger is the disparity magnitude and the more difficult it is to fuse the stereoscopic images.” The phenomenon is “consistent with the common knowledge that as an object is brought within arm’s length and moved closer and closer towards the eyes the effort to maintain binocular fixation on the object increases and becomes stressful,” it said. “Crosstalk” is often said to contribute to visual discomfort when viewing 3D, but there’s “meager” scientific evidence to support the claim, the document said. “Studies are required to look at the impact of long-term viewing that takes into consideration the viewing habits of television owners."

There’s little consensus on the best ways to test 3D or the methodologies that should be used, the report said. “It is difficult to carry out a long-term viewing study on visual comfort,” it said. “Aside from ethical issues, there are various questions that need to be tackled. What should the contents of the test sequences consist of? What should be the viewing conditions, such as ambient lighting, display size and viewing distance? How to ensure the safety of viewers who are being tested? In selecting viewers for the study, what should be the viewer characteristics, such as age and previous 3D viewing experience?” There’s also no standard objective or subjective way to measure “visual comfort for long-term viewing of stereoscopic images,” the report said.