DYNAMIC CUES TO DEPTH PERCEPTION
Qualitative work has demonstrated that children or adults who are diagnosed as stereo-blind when assessed using standard clinical tests report the enhanced perception of depth when viewing dynamic stereoscopic stimuli such as 3D films. One possibility is that stereoblind observers have some residual stereovision which is not revealed in classical tests that usually use static stimuli.
The purpose of this study was to investigate whether dynamic disparity information is more effective for extracting depth-from-disparity, and if so, to characterise the nature of these dynamic stereo-mechanisms. We therefore looked at different dynamic disparity conditions: a z-location change, i.e. an object coming towards the observer with a concordant disparity increase; an x-motion change, i.e. an object moves laterally while the disparity changes.
Our main finding is that observers are most sensitive to z-location changes which is reflected in lower disparity thresholds (~300 arc sec). When the same disparity is applied to a pattern moving from right to left (x-location change), observers are no better in detecting the depth change as they are for static stimuli (~420 arc sec). We therefore conclude that it is not the dynamic disparity information per se that’s important, but the disparity change needs to be consistent with the direction of motion.
Our findings have implications for neurobiological models of binocular vision by providing useful constraints on the relative importance of static vs dynamic disparity signals for depth perception. Dynamic disparity changes (condition: Z-LOCATION CHANGE) are ecologically valid signals that arise either from self-motion or from object motion towards the observer; our data show that these dynamic disparity signals are associated with the highest performance for depth detection, consistent with their ecological validity.
Given the omission of changes of disparity, currently used static stereoacuity tests may underestimate the degree of binocular function. With this in mind, the present study constitutes an important first step toward the development of a clinically useful test of dynamic stereoacuity, to reflect real world interactions with depth.
Understanding the differential processing of static and dyamic cues in the human stereo system might also guide us in the design of stereoscopic 3D content with the aim to maximise viewing comfort and to minimise distortions.
Laurence Tidbury, Orthoptics and Vision Science, University of Liverpool
Anna O’Connor, Orthoptics and Vision Science, University of Liverpool
1. Tidbury, Laurence, Anna R. O’Connor, Kevin R. Brooks, Sophie M. Wuerger: A systematic comparison of static and dynamic cues to depth, Invest Ophthalmol Vis Sci, 57(8), 3545-3553. https://doi:10.1167/iovs.15-18104
2. Tidbury, L. P., O’Connor, A. R., & Wuerger, S. M. (2019). The effect of induced fusional demand on static and dynamic stereoacuity thresholds: the digital Synoptophore. BMC Ophthalmology, 19(1), 6.
Acknowledgement of Support
ESRC #1265972 (Laurence Tidbury)
EPSRC #1126452 (Rob Black; with SONY)