Abstract
Recent advances in film capture and display technologies have made it possible to use frame rates much higher than the 24fps convention. It is assumed that high frame rates (HFR) will enhance perception of motion in 2-D and 3-D media. The goal of this project is to assess this assumption empirically. In a series of experiments we measured lateral (2-D) and in depth (3-D) global motion coherence thresholds using random-dot patterns in a mirror stereoscope and a 3D projection system. The refresh rate of the display was fixed at 96 Hz, and we manipulated the flash protocol to create 96fps (single flash), 48fps (double flash) and 24fps (quadruple flash). Simulated linear velocity of the elements through space was equated in the 2-D and 3-D conditions. Conditions were randomly interleaved using the method of constant stimuli and a two-interval forced-choice procedure to measure the proportion of coherent elements required to reliably detect global motion. Results from six observers showed no consistent effect of flash protocol on coherence thresholds in either the 2-D or the 3-D test conditions. Interestingly, the 3-D task was considerably harder for all observers and required longer viewing time. Even with the increased viewing time, thresholds were double those seen in the lateral motion condition, despite the fact that the velocity of element motion through space was the same in the two conditions. Our results show that while frame rate influences local 2-D motion processing, it has no apparent impact on lateral, or in depth, global motion perception.