Lr. Ziegler et al., Local luminance factors that determine the maximum disparity for seeing cyclopean surface shape, VISION RES, 40(9), 2000, pp. 1157-1165
We measured the maximum disparity grating amplitude (d(max)) for seeing cyc
lopean surface shape, using stereograms made from dense arrays of micropatt
erns, whose luminance characteristics were manipulated. In Experiment 1, we
used disparity gratings made from Gabor micropatterns. D-max was found to
vary inversely both with luminance spatial frequency and with Gabor size, b
ut was constant for a constant bandwidth (frequency times size). To test wh
ether this was due to changes in bandwidth per se or to changes in the numb
er of local features, in Experiment 2 we manipulated the local feature cont
ent with a range of micropatterns that we termed 'edgels'. The results supp
orted neither hypothesis. In Experiment 3 we varied the phases of the Fouri
er components of square wave edgels, thereby introducing more features, and
we found that this did not change d(max). Taken together, our results show
that d(max) decreases with an increase in the number of local luminance cy
cles at each luminance scale. D-max is mainly limited by false target match
ing between similar components of the micropatterns. Stereopis, in terms of
surface shape perception, is served only by first order mechanisms, and on
ly by luminance filters that are broadband. (C) 2000 Elsevier Science Ltd.
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