This is a slide shown by Phil Corriveau, Principal Engineer at Intel Corporation, an experimental psychologist who is human factors chair of the 3D @ home consortium. It depicts the buzz about stereoscopic 3D (S3D) and what gets filled inside the bubbles above very much depends on the user experience. It is a marriage between psychology and psychophysics. Phil talked about the concept of flow, with a focused, centered, immersion, almost like the S3D version of Mihaly Csikszentmihalyi.
Where is the bar set for palatable user experience? Roughly 80% of the viewers of S3D technology will find it cool, even awesome, and rewarding. It is estimated however that a full 20% will find have issues with S3D ranging from difficulty in perceiving the effects to difficulty in the ability to view without experiencing discomfort or dizziness. Phil was one of the outstanding speakers at yesterday morning’s AOA special session on S3D, and you can view the course outline here.
Dr. Jim Sheedy, who was also interviewed by NBC in Chicago during the AOA meeting, did a superb job of shaping and leading off the program. He noted that stereoacuity is a relative form of depth layered on top of monocular cues. Most S3D films work with what is called a disparity budget. Most films will work within a disparity range of only 3 to 4% between the two eyes, as more than that tends to induce discomfort in normal viewers. The disparity or depth budget is something a stereographer will plot out much as a composer might script sound for a movie to balance crescendo and volume to match the emotional tone of various scenes.
What’s really amazing is that to work within that 3 to 4% disparity budget during a film, the vergence system is only changing about two-thirds of a prism diopter to maintain fusion and register S3D. So what’s all the fuss about binocular vision and these dizzying effects of watching S3D? Well first of all, we make the assumption that accommodation is going to stay on the plane of the viewing screen the entire time while vergence runs wild. Nice assumption, but this isn’t always the case – and viewers who have accommodative-vergence integrative problems are likely to perceive variable blur, or at least asthenopia as their brain tries to figure out what’s going on.
Here is a depiction of the challenge in de-coupling accommodation from vergence. It was taken from a wonderful article by Held and Hui on a guide to stereoscopic 3D displays in medicine.
As Dr. Dominick Maino noted in his presentation yesterday, there is a certain amount of cognitive dissonance in the brain believing that accommodation and vergence are not supposed to be at the same plane. As long as 15 years ago it was recognized that accommodation had trouble staying put when vergence was being manipulated independently.