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Matteo Toscani, Sunčica Zdravković, Karl Gegenfurtner; Viewing strategies that aid lightness constancy in dynamic scenes. Journal of Vision 2015;15(12):629. doi: 10.1167/15.12.629.
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© ARVO (1962-2015); The Authors (2016-present)
Lightness of a surface depends on luminance sampled trough fixations (Toscani et al.,2013). This information changes when the surface moves across a light field and so do lightness matches (Zdravkovic, 2008). We studied luminance integration over time and space in a lightness matching task. A pendulum was presented in a virtual scene with clearly visible decreasing illumination from left to right. Observers either freely looked at the scene or had to fixate a spot on a dark or light region on the pendulum for the whole duration of each trial. The pendulum either moved across the whole scene starting from the light or the dark side or was kept motionless in these two regions of interest. The pendulum was matched lighter when observers were forced to fixate a light region than a dark one, showing that fixation positions do influence perceived lightness. Observers produced lighter matches when the pendulum was on the lighter side of the scene than when it was on the darker side. Lighter matches were also obtained when the pendulum moved from dark to light, as compared to the other way around. When eye movements were not constrained, this difference was less pronounced. In free viewing, observers tended to adjust their fixation positions as to counteract the illumination difference, preferring lighter regions on the pendulum when it was on the darker side and vice versa.Eye movements seem to play a compensatory role for illumination changes due to object motion. Our results emphasize the importance of fixation positions for achieving perceptual stability.
Meeting abstract presented at VSS 2015
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