Лекция "Восприятие цвета и изображений" Qasim Zaidi

To illustrate the uses of geometry in understanding visual perception, I will present studies onperception of pictures and colors:

(i) We show that in both 3D scene understanding and picture perception, observers mentallyapply projective geometry to retinal images. Reliance on the same geometrical function isrevealed by the surprisingly close agreement between observers in making judgments of 3Dobject poses. These judgments are in accordance with that predicted by a back-projection fromretinal orientations to 3D poses, but are distorted by a bias to see poses as closer to frontoparallel.Reliance on retinal images explains distortions in perceptions of real scenes, andinvariance in pictures, including the classical conundrum of why certain image features alwayspoint at the observer regardless of viewpoint. These results have implications for investigating3D scene inferences in biological systems, and designing machine vision systems.

(ii) Geometrical spaces based on similarity judgments are widely used to represent importantstimulus qualities in perception, visual cognition and neuroscience. We introduce an approachto measuring relative similarities, which enables us to test the underlying geometry of aperceptual space and its mapping to a physical space of stimuli. For color perception, ourresults show that perceptual geometry depends on the mental representation used in judgingsimilarity, and it has an affine structure when observers use an opponent-color representation.An affine geometry implies that neural coding of similarity could involve simple ratios ofresponses. Our measurements also reveal that the uniform color spaces CIELAB and CIELUV,used extensively in industrial applications, do not provide adequate representation of similaritybetween moderately spaced colors.