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Disparity statistics in natural scenes
Y. Liu, L.K. Cormack and A.C. Bovik
Journal of Vision
Abstract
Binocular disparity is the input to stereopsis, which is a very strong depth cue in humans. However, the distribution of
binocular disparities in natural environments has not been quantitatively measured. In this study, we converted distances
from accurate range maps of forest scenes and indoor scenes into the disparities that an observer would encounter, given
an eye model and fixation distances (which we measured for the forest environment, and simulated for the indoor
environment). We found that the distributions of natural disparities in these two kinds of scenes are centered at zero, have
high peaks, and span about 5 deg, which closely matches the macaque MT cells’ disparity tuning range. These ranges are
fully within the operational range of human stereopsis determined psychophysically. Suprathreshold disparities (910 arcsec)
are common rather than exceptional. There is a prevailing notion that stereopsis only operates within a few meters, but our
finding suggests that we should rethink the role of stereopsis at far viewing distances because of the abundance of
suprathreshold disparities.
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