Stereopsis for rapidly moving targets

Stereoscopic depth perception is possible with luminance-defined target velocities at least as high as 600° s−1, up to the limit of 30 Hz imposed by the high-temporal frequency cut-off of the eye. The limitation for perceiving depth from stereo disparity of moving targets is not their velocity but the temporal frequency bandwidth of the eye, which is affected by adaption state. Stereoacuity for a depth shift in a horizontally moving grating depends not on spatial disparity between corresponding luminance points in spatial units of arc min, but on the spatial shift as a fixed proportion of the period of the grating, in other words, on the phase angle difference between the two eyes, as is also the case for obliquely orientated, stationary gratings. Phase differences explain not only the classic Pulfrich stereophenomenon but its equivalent with dynamic visual noise, and a new effect in which depth results from interocular phase differences in luminance modulation. This article is part of a discussion meeting issue ‘New approaches to 3D vision’.