This pair of videos demonstrates
the striking differences in spatial and temporal sensitivity
associated with luminance and disparity processing. The spatial
frequency units were calculated for a viewing distance of 3.5
times picture height. The files are .MP4 and can be run in
QuickTime or VLC.
Note: People with
photosensitive epilepsy should consider not viewing the
videos.
LUMINANCE VIDEO [.MP4}
This video depicts a luminance
grating with spatial frequency increasing from 0.06 to 3cpd from
bottom to top and contrast increasing from ~0 to ~1 from left to
right. The grating alternates in counter-phase at different
temporal frequencies over time; the current alternation rate (0,
0.94, 1.87, 3.75, 7.5, or 15Hz) is indicated in the upper left
corner (if number is not visible, move cursor outside window). The
grating is visible at high contrast at all spatial and temporal
frequencies (right side) and less visible or invisible at low
contrast. There is little effect of spatial and temporal frequency
because the range of frequencies is small relative to the
spatio-temporal contrast sensitivity function.
DISPARITY VIDEO [.MP4]
This video shows a
disparity-defined corrugation with the same spatial and temporal
frequencies as in the upper video. Cross-fuse to see
stereoscopically. The spatial frequencies are correct when viewing
distance is 3.5 times picture height. Corrugation spatial
frequency increases from 0.06 to 3cpd from bottom to top.
Disparity amplitude increases from 0 to 1.75° from left to right.
Again the current temporal frequency is indicated in the upper
left corner (if number is not visible, move cursor outside
window). Unlike the luminance grating, the disparity corrugation
cannot be seen in the upper right corner where the disparity
amplitude exceeds the disparity-gradient limit. The region where
it becomes invisible increases in size as temporal frequency
increases because visibility is limited by the spatio-temporal
disparity-gradient limit.