Brightness and Contrast

Nigel Daw

in How Vision Works

Published in print January 2012 | ISBN: 9780199751617
Published online May 2012 | e-ISBN: 9780199932375 | DOI:
Brightness and Contrast

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The lightness of an object is determined in relation to the objects around it. The overall illumination of the scene is ignored, and so are shadows falling across the object, and curvature of the object. The lightness is thus calculated by the sharp changes at boundaries, and the slow changes across the object are ignored. The process is started in the retina, where cells respond to contrast with the immediate surround, and continued in visual cortex where influences from a wider area come in. Further influences, such as the effect of perception of transparency, probably come in at higher levels of the system.

Keywords: lightness; surround; shadows; transparency; curvature; retina; lateral geniculate; visual cortex

Chapter.  4558 words.  Illustrated.

Subjects: Neuropsychology

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