The effect of image disparity, convergence distance and focal length on perceived quality in stereoscopic displays

Within the area of broadcasting and entertainment, stereoscopic displays are used to heighten the viewer's sense of excitement and qual ity. To evaluate these subjective experiences, an appreciation-oriented approach may be appropriate. Within this context, the current study investigates the influence of image disparity, convergence distance and focal length on the subjective assessment of depth, naturalness of depth and quality of depth. Twelve observers viewed a set of stereoscopic still images varying in image disparity, convergence distance and focal length. Each observer was asked to rate his/her impression of depth, naturalness of depth and quality of depth, in separate counterbalanced sessions. Results indicate that observers prefer a stereoscopic presentation of images over a monoscopic presentation. A clear optimum was found at 4 em image disparity for both subjective judgments of naturalness and of quality. A focal length effect was only found for extreme image disparities. Although there was a strong linear relationship between naturalness and quality (a correlation of r=O.96), a small but systematic deviation could be observed. This quality-naturalness shift is discussed in relation to similar, yet more pronounced findings in the domain of colour perception.