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Nobuaki Ito, Takao Sato; The chromatic contribution to the human stereo system measured with a depth-canceling technique. Journal of Vision 2001;1(3):174. doi: 10.1167/1.3.174.
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© ARVO (1962-2015); The Authors (2016-present)
It has been known that stereo system receives little chromatic input, but evidences on this point have been mostly qualitative. In motion, however, Cavanagh & Anstis (1991) used a canceling paradigm in which they antagonized opposite directional motions, and found that the chromatic contribution to motion system is about 12% of that of luminance. In this study, we employed a similar cancellation method and quantitatively assessed chromatic contribution to stereo system. We used a new stimulus called dynamic random-phase stereograms (DRPS), a 1D version of dynamic random-dot stereograms. In each image of these stimuli, two pairs of red and green vertical sinusoidal gratings (1 c/d, presumably no aberration) were overlapped with particular phase relations. In one pair (L), the R/G gratings were in phase to create luminance grating, and, in the other (L+C), R/G gratings with different mean luminance were placed anti-phase, thus it has chromatic and luminance components. Spatial phase of L and L+C pairs were randomly shifted at 33.3 Hz, while the phase differences for C and L+C pairs between the two binocular images, i.e. disparities, were kept constant. The two binocular pairs had disparity of opposite signs. Subjects discriminated the depth of the image relative to surrounding frame while luminance component of L+C pair was varied systematically to find the canceling points. From the canceling data obtained with L pair contrast of 0.35 to 0.5, equivalence luminance contrast (chromatic contribution to stereo system) was calculated. The obtained equivalent luminance contrast was about 0.2, which is quite similar to that for motion suggesting an important similarity between the two systems. The results also indicated that this canceling technique is quite effective in quantitative analysis of chromatic contribution to stereo as well as motion system.
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